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	$187.44	4.601%	$196.0641	$196.06	$196.05	$196.10
Purchase #2	$209.99	12.284%	$235.7852	$235.79	$235.80	$235.80
Purchase #3	$239.99	11.198%	$266.8641	$266.86	$266.85	$266.90
Purchase #4	$154.34	9.301%	$168.6952	$168.70	$168.70	$168.70
Purchase #5	$67.56	7.107%	$72.3615	$72.36	$72.35	$72.40
Purchase #6	$232.40	10.394%	$256.5557	$256.56	$256.55	$256.60
Purchase #7	$40.62	12.734%	$45.7926	$45.79	$45.80	$45.80
7 purchase totals =	$1,132.34		$1,242.1184	$1,242.12	$1,242.10	$1,242.30