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	$240.47	10.133%	$264.8368	$264.84	$264.85	$264.80
Purchase #2	$196.37	7.507%	$211.1115	$211.11	$211.10	$211.10
Purchase #3	$67.82	6.574%	$72.2785	$72.28	$72.30	$72.30
Purchase #4	$51.99	3.586%	$53.8544	$53.85	$53.85	$53.90
Purchase #5	$242.47	3.358%	$250.6121	$250.61	$250.60	$250.60
Purchase #6	$65.31	9.760%	$71.6843	$71.68	$71.70	$71.70
Purchase #7	$218.57	4.223%	$227.8002	$227.80	$227.80	$227.80
7 purchase totals =	$1,083.00		$1,152.1778	$1,152.17	$1,152.20	$1,152.20