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	$161.41	11.403%	$179.8156	$179.82	$179.80	$179.80
Purchase #2	$39.35	13.225%	$44.554	$44.55	$44.55	$44.60
Purchase #3	$232.58	4.428%	$242.8786	$242.88	$242.90	$242.90
Purchase #4	$97.98	11.806%	$109.5475	$109.55	$109.55	$109.50
Purchase #5	$54.90	12.834%	$61.9459	$61.95	$61.95	$61.90
Purchase #6	$167.49	5.114%	$176.0554	$176.06	$176.05	$176.10
Purchase #7	$158.68	13.489%	$180.0843	$180.08	$180.10	$180.10
7 purchase totals =	$912.39		$994.8813	$994.89	$994.90	$994.90