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	$211.62	4.362%	$220.8509	$220.85	$220.85	$220.90
Purchase #2	$100.54	5.874%	$106.4457	$106.45	$106.45	$106.40
Purchase #3	$57.47	4.280%	$59.9297	$59.93	$59.95	$59.90
Purchase #4	$57.30	8.370%	$62.096	$62.10	$62.10	$62.10
Purchase #5	$7.63	11.816%	$8.5316	$8.53	$8.55	$8.50
Purchase #6	$19.88	13.236%	$22.5113	$22.51	$22.50	$22.50
Purchase #7	$145.56	3.305%	$150.3708	$150.37	$150.35	$150.40
7 purchase totals =	$600.00		$630.7360	$630.74	$630.75	$630.70