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	$161.88	10.269%	$178.5035	$178.50	$178.50	$178.50
Purchase #2	$122.34	11.218%	$136.0641	$136.06	$136.05	$136.10
Purchase #3	$223.39	10.728%	$247.3553	$247.36	$247.35	$247.40
Purchase #4	$151.59	13.735%	$172.4109	$172.41	$172.40	$172.40
Purchase #5	$16.73	10.725%	$18.5243	$18.52	$18.50	$18.50
Purchase #6	$139.29	11.743%	$155.6468	$155.65	$155.65	$155.60
Purchase #7	$98.80	7.814%	$106.5202	$106.52	$106.50	$106.50
7 purchase totals =	$914.02		$1,015.0251	$1,015.02	$1,014.95	$1,015.00