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	$106.96	3.151%	$110.3303	$110.33	$110.35	$110.30
Purchase #2	$128.40	13.124%	$145.2512	$145.25	$145.25	$145.30
Purchase #3	$151.46	8.411%	$164.1993	$164.20	$164.20	$164.20
Purchase #4	$40.47	9.651%	$44.3758	$44.38	$44.40	$44.40
Purchase #5	$120.33	3.461%	$124.4946	$124.49	$124.50	$124.50
Purchase #6	$23.80	8.869%	$25.9108	$25.91	$25.90	$25.90
Purchase #7	$53.41	11.507%	$59.5559	$59.56	$59.55	$59.60
7 purchase totals =	$624.83		$674.1179	$674.12	$674.15	$674.20