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	$228.38	6.428%	$243.0603	$243.06	$243.05	$243.10
Purchase #2	$238.46	6.565%	$254.1149	$254.11	$254.10	$254.10
Purchase #3	$50.92	5.181%	$53.5582	$53.56	$53.55	$53.60
Purchase #4	$186.79	13.562%	$212.1225	$212.12	$212.10	$212.10
Purchase #5	$105.96	10.840%	$117.4461	$117.45	$117.45	$117.40
Purchase #6	$70.46	7.142%	$75.4923	$75.49	$75.50	$75.50
Purchase #7	$90.49	10.222%	$99.7399	$99.74	$99.75	$99.70
7 purchase totals =	$971.46		$1,055.5342	$1,055.53	$1,055.50	$1,055.50