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	$131.96	9.374%	$144.3299	$144.33	$144.35	$144.30
Purchase #2	$215.62	3.155%	$222.4228	$222.42	$222.40	$222.40
Purchase #3	$13.66	13.637%	$15.5228	$15.52	$15.50	$15.50
Purchase #4	$121.34	3.520%	$125.6112	$125.61	$125.60	$125.60
Purchase #5	$148.58	11.655%	$165.897	$165.90	$165.90	$165.90
Purchase #6	$243.77	8.511%	$264.5173	$264.52	$264.50	$264.50
Purchase #7	$170.42	7.466%	$183.1436	$183.14	$183.15	$183.10
7 purchase totals =	$1,045.35		$1,121.4446	$1,121.44	$1,121.40	$1,121.30