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	$227.84	9.326%	$249.0884	$249.09	$249.10	$249.10
Purchase #2	$57.47	13.766%	$65.3813	$65.38	$65.40	$65.40
Purchase #3	$247.65	7.128%	$265.3025	$265.30	$265.30	$265.30
Purchase #4	$80.37	3.122%	$82.8792	$82.88	$82.90	$82.90
Purchase #5	$44.25	8.593%	$48.0524	$48.05	$48.05	$48.10
Purchase #6	$228.77	11.315%	$254.6553	$254.66	$254.65	$254.70
Purchase #7	$112.94	12.809%	$127.4065	$127.41	$127.40	$127.40
7 purchase totals =	$999.29		$1,092.7656	$1,092.77	$1,092.80	$1,092.90