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	$231.46	8.404%	$250.9119	$250.91	$250.90	$250.90
Purchase #2	$145.96	8.777%	$158.7709	$158.77	$158.75	$158.80
Purchase #3	$32.40	11.624%	$36.1662	$36.17	$36.15	$36.20
Purchase #4	$56.32	4.474%	$58.8398	$58.84	$58.85	$58.80
Purchase #5	$111.74	4.382%	$116.6364	$116.64	$116.65	$116.60
Purchase #6	$212.72	7.873%	$229.4674	$229.47	$229.45	$229.50
Purchase #7	$183.37	9.238%	$200.3097	$200.31	$200.30	$200.30
7 purchase totals =	$973.97		$1,051.1023	$1,051.11	$1,051.05	$1,051.10