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	$10.77	5.464%	$11.3585	$11.36	$11.35	$11.40
Purchase #2	$62.87	7.745%	$67.7393	$67.74	$67.75	$67.70
Purchase #3	$107.83	3.268%	$111.3539	$111.35	$111.35	$111.40
Purchase #4	$77.89	7.107%	$83.4256	$83.43	$83.45	$83.40
Purchase #5	$155.86	6.323%	$165.715	$165.72	$165.70	$165.70
Purchase #6	$103.63	5.493%	$109.3224	$109.32	$109.30	$109.30
Purchase #7	$236.29	5.133%	$248.4188	$248.42	$248.40	$248.40
7 purchase totals =	$755.14		$797.3335	$797.34	$797.30	$797.30