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	$96.46	7.240%	$103.4437	$103.44	$103.45	$103.40
Purchase #2	$70.84	10.530%	$78.2995	$78.30	$78.30	$78.30
Purchase #3	$95.96	11.338%	$106.8399	$106.84	$106.85	$106.80
Purchase #4	$191.74	12.504%	$215.7152	$215.72	$215.70	$215.70
Purchase #5	$82.53	5.515%	$87.0815	$87.08	$87.10	$87.10
Purchase #6	$205.97	7.852%	$222.1428	$222.14	$222.15	$222.10
Purchase #7	$190.83	10.452%	$210.7756	$210.78	$210.80	$210.80
7 purchase totals =	$934.33		$1,024.2982	$1,024.30	$1,024.35	$1,024.20