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	$182.35	4.289%	$190.171	$190.17	$190.15	$190.20
Purchase #2	$63.72	5.439%	$67.1857	$67.19	$67.20	$67.20
Purchase #3	$71.78	13.342%	$81.3569	$81.36	$81.35	$81.40
Purchase #4	$80.37	3.761%	$83.3927	$83.39	$83.40	$83.40
Purchase #5	$151.69	13.654%	$172.4018	$172.40	$172.40	$172.40
Purchase #6	$106.64	12.609%	$120.0862	$120.09	$120.10	$120.10
Purchase #7	$20.55	3.796%	$21.3301	$21.33	$21.35	$21.30
7 purchase totals =	$677.10		$735.9244	$735.93	$735.95	$736.00