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	$178.69	12.368%	$200.7904	$200.79	$200.80	$200.80
Purchase #2	$134.50	5.270%	$141.5882	$141.59	$141.60	$141.60
Purchase #3	$106.80	5.358%	$112.5223	$112.52	$112.50	$112.50
Purchase #4	$147.67	13.313%	$167.3293	$167.33	$167.35	$167.30
Purchase #5	$171.93	5.637%	$181.6217	$181.62	$181.60	$181.60
Purchase #6	$204.69	3.687%	$212.2369	$212.24	$212.25	$212.20
Purchase #7	$165.78	7.662%	$178.4821	$178.48	$178.50	$178.50
7 purchase totals =	$1,110.06		$1,194.5709	$1,194.57	$1,194.60	$1,194.50