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	$188.35	4.149%	$196.1646	$196.16	$196.15	$196.20
Purchase #2	$182.37	7.227%	$195.5499	$195.55	$195.55	$195.50
Purchase #3	$94.34	5.306%	$99.3457	$99.35	$99.35	$99.30
Purchase #4	$28.80	8.650%	$31.2912	$31.29	$31.30	$31.30
Purchase #5	$242.69	3.335%	$250.7837	$250.78	$250.80	$250.80
Purchase #6	$188.74	11.710%	$210.8415	$210.84	$210.85	$210.80
Purchase #7	$213.68	11.869%	$239.0417	$239.04	$239.05	$239.00
7 purchase totals =	$1,138.97		$1,223.0183	$1,223.01	$1,223.05	$1,222.90