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	$158.67	5.457%	$167.3286	$167.33	$167.35	$167.30
Purchase #2	$65.96	11.608%	$73.6166	$73.62	$73.60	$73.60
Purchase #3	$52.63	13.844%	$59.9161	$59.92	$59.90	$59.90
Purchase #4	$52.55	11.792%	$58.7467	$58.75	$58.75	$58.70
Purchase #5	$32.51	3.258%	$33.5692	$33.57	$33.55	$33.60
Purchase #6	$123.89	11.567%	$138.2204	$138.22	$138.20	$138.20
Purchase #7	$119.84	3.417%	$123.9349	$123.93	$123.95	$123.90
7 purchase totals =	$606.05		$655.3325	$655.34	$655.30	$655.20