Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$161.40	3.560%	$167.1458	$167.15	$167.15	$167.10
Purchase #2	$182.83	11.728%	$204.2723	$204.27	$204.25	$204.30
Purchase #3	$245.51	7.279%	$263.3807	$263.38	$263.40	$263.40
Purchase #4	$110.87	11.662%	$123.7997	$123.80	$123.80	$123.80
Purchase #5	$171.73	9.380%	$187.8383	$187.84	$187.85	$187.80
Purchase #6	$236.91	11.260%	$263.5861	$263.59	$263.60	$263.60
Purchase #7	$194.56	11.797%	$217.5122	$217.51	$217.50	$217.50
7 purchase totals =	$1,303.81		$1,427.5351	$1,427.54	$1,427.55	$1,427.50