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	$138.77	9.848%	$152.4361	$152.44	$152.45	$152.40
Purchase #2	$53.51	10.173%	$58.9536	$58.95	$58.95	$59.00
Purchase #3	$68.38	4.477%	$71.4414	$71.44	$71.45	$71.40
Purchase #4	$53.81	4.631%	$56.3019	$56.30	$56.30	$56.30
Purchase #5	$57.98	12.624%	$65.2994	$65.30	$65.30	$65.30
Purchase #6	$228.56	6.462%	$243.3295	$243.33	$243.35	$243.30
Purchase #7	$57.88	11.139%	$64.3273	$64.33	$64.35	$64.30
7 purchase totals =	$658.89		$712.0892	$712.09	$712.15	$712.00