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	$229.54	7.142%	$245.9337	$245.93	$245.95	$245.90
Purchase #2	$113.51	12.203%	$127.3616	$127.36	$127.35	$127.40
Purchase #3	$115.77	12.692%	$130.4635	$130.46	$130.45	$130.50
Purchase #4	$111.26	5.669%	$117.5673	$117.57	$117.55	$117.60
Purchase #5	$168.80	9.648%	$185.0858	$185.09	$185.10	$185.10
Purchase #6	$233.52	6.751%	$249.2849	$249.28	$249.30	$249.30
Purchase #7	$50.62	3.379%	$52.3304	$52.33	$52.35	$52.30
7 purchase totals =	$1,023.02		$1,108.0272	$1,108.02	$1,108.05	$1,108.10