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	$223.69	4.792%	$234.4092	$234.41	$234.40	$234.40
Purchase #2	$101.92	3.668%	$105.6584	$105.66	$105.65	$105.70
Purchase #3	$75.97	8.861%	$82.7017	$82.70	$82.70	$82.70
Purchase #4	$237.83	11.127%	$264.2933	$264.29	$264.30	$264.30
Purchase #5	$242.82	7.601%	$261.2767	$261.28	$261.30	$261.30
Purchase #6	$174.54	5.121%	$183.4782	$183.48	$183.50	$183.50
Purchase #7	$6.82	6.871%	$7.2886	$7.29	$7.30	$7.30
7 purchase totals =	$1,063.59		$1,139.1061	$1,139.11	$1,139.15	$1,139.20