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	$53.90	10.445%	$59.5299	$59.53	$59.55	$59.50
Purchase #2	$226.28	9.719%	$248.2722	$248.27	$248.25	$248.30
Purchase #3	$123.94	3.396%	$128.149	$128.15	$128.15	$128.10
Purchase #4	$20.31	9.516%	$22.2427	$22.24	$22.25	$22.20
Purchase #5	$152.68	3.521%	$158.0559	$158.06	$158.05	$158.10
Purchase #6	$22.48	7.204%	$24.0995	$24.10	$24.10	$24.10
Purchase #7	$75.68	13.480%	$85.8817	$85.88	$85.90	$85.90
7 purchase totals =	$675.27		$726.2309	$726.23	$726.25	$726.20