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	$57.80	6.500%	$61.557	$61.56	$61.55	$61.60
Purchase #2	$223.53	12.675%	$251.8624	$251.86	$251.85	$251.90
Purchase #3	$134.54	13.115%	$152.1849	$152.18	$152.20	$152.20
Purchase #4	$180.25	5.495%	$190.1547	$190.15	$190.15	$190.20
Purchase #5	$187.93	11.386%	$209.3277	$209.33	$209.35	$209.30
Purchase #6	$55.44	11.533%	$61.8339	$61.83	$61.85	$61.80
Purchase #7	$131.30	12.160%	$147.2661	$147.27	$147.25	$147.30
7 purchase totals =	$970.79		$1,074.1867	$1,074.18	$1,074.20	$1,074.30