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	$44.90	8.672%	$48.7937	$48.79	$48.80	$48.80
Purchase #2	$92.84	7.136%	$99.4651	$99.47	$99.45	$99.50
Purchase #3	$204.96	8.242%	$221.8528	$221.85	$221.85	$221.90
Purchase #4	$181.62	8.450%	$196.9669	$196.97	$196.95	$197.00
Purchase #5	$153.93	5.514%	$162.4177	$162.42	$162.40	$162.40
Purchase #6	$238.79	4.706%	$250.0275	$250.03	$250.05	$250.00
Purchase #7	$149.62	10.515%	$165.3525	$165.35	$165.35	$165.40
7 purchase totals =	$1,066.66		$1,144.8762	$1,144.88	$1,144.85	$1,145.00