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	$140.47	11.591%	$156.7519	$156.75	$156.75	$156.80
Purchase #2	$221.53	7.851%	$238.9223	$238.92	$238.90	$238.90
Purchase #3	$67.87	6.407%	$72.2184	$72.22	$72.20	$72.20
Purchase #4	$151.43	4.462%	$158.1868	$158.19	$158.20	$158.20
Purchase #5	$229.52	11.715%	$256.4083	$256.41	$256.40	$256.40
Purchase #6	$244.87	13.435%	$277.7683	$277.77	$277.75	$277.80
Purchase #7	$23.83	10.274%	$26.2783	$26.28	$26.30	$26.30
7 purchase totals =	$1,079.52		$1,186.5343	$1,186.54	$1,186.50	$1,186.60