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	$231.83	5.324%	$244.1726	$244.17	$244.15	$244.20
Purchase #2	$59.79	13.614%	$67.9298	$67.93	$67.95	$67.90
Purchase #3	$210.31	5.549%	$221.9801	$221.98	$222.00	$222.00
Purchase #4	$134.83	12.389%	$151.5341	$151.53	$151.55	$151.50
Purchase #5	$69.27	5.345%	$72.9725	$72.97	$72.95	$73.00
Purchase #6	$143.52	4.454%	$149.9124	$149.91	$149.90	$149.90
Purchase #7	$88.53	3.742%	$91.8428	$91.84	$91.85	$91.80
7 purchase totals =	$938.08		$1,000.3443	$1,000.33	$1,000.35	$1,000.30