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	$98.40	13.234%	$111.4223	$111.42	$111.40	$111.40
Purchase #2	$194.38	5.558%	$205.1836	$205.18	$205.20	$205.20
Purchase #3	$100.71	10.612%	$111.3973	$111.40	$111.40	$111.40
Purchase #4	$129.65	8.370%	$140.5017	$140.50	$140.50	$140.50
Purchase #5	$171.56	9.729%	$188.2511	$188.25	$188.25	$188.30
Purchase #6	$79.86	6.654%	$85.1739	$85.17	$85.15	$85.20
Purchase #7	$150.77	10.736%	$166.9567	$166.96	$166.95	$167.00
7 purchase totals =	$925.33		$1,008.8866	$1,008.88	$1,008.85	$1,009.00