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	$79.91	6.421%	$85.041	$85.04	$85.05	$85.00
Purchase #2	$58.90	5.584%	$62.189	$62.19	$62.20	$62.20
Purchase #3	$225.93	9.717%	$247.8836	$247.88	$247.90	$247.90
Purchase #4	$15.40	4.719%	$16.1267	$16.13	$16.15	$16.10
Purchase #5	$188.39	4.186%	$196.276	$196.28	$196.30	$196.30
Purchase #6	$233.77	5.155%	$245.8208	$245.82	$245.80	$245.80
Purchase #7	$154.43	7.234%	$165.6015	$165.60	$165.60	$165.60
7 purchase totals =	$956.73		$1,018.9386	$1,018.94	$1,019.00	$1,018.90