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	$105.49	10.479%	$116.5443	$116.54	$116.55	$116.50
Purchase #2	$97.25	12.767%	$109.6659	$109.67	$109.65	$109.70
Purchase #3	$235.43	3.253%	$243.0885	$243.09	$243.10	$243.10
Purchase #4	$162.73	6.858%	$173.89	$173.89	$173.90	$173.90
Purchase #5	$150.85	10.557%	$166.7752	$166.78	$166.80	$166.80
Purchase #6	$128.91	8.501%	$139.8686	$139.87	$139.85	$139.90
Purchase #7	$229.29	10.873%	$254.2207	$254.22	$254.20	$254.20
7 purchase totals =	$1,109.95		$1,204.0532	$1,204.06	$1,204.05	$1,204.10