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	$54.30	13.339%	$61.5431	$61.54	$61.55	$61.50
Purchase #2	$234.53	10.577%	$259.3362	$259.34	$259.35	$259.30
Purchase #3	$240.81	7.537%	$258.9598	$258.96	$258.95	$259.00
Purchase #4	$162.95	13.141%	$184.3633	$184.36	$184.35	$184.40
Purchase #5	$142.63	13.781%	$162.2858	$162.29	$162.30	$162.30
Purchase #6	$85.77	6.179%	$91.0697	$91.07	$91.05	$91.10
Purchase #7	$159.94	5.375%	$168.5368	$168.54	$168.55	$168.50
7 purchase totals =	$1,080.93		$1,186.0947	$1,186.10	$1,186.10	$1,186.10