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	$140.96	7.108%	$150.9794	$150.98	$151.00	$151.00
Purchase #2	$223.45	12.758%	$251.9578	$251.96	$251.95	$252.00
Purchase #3	$35.69	10.609%	$39.4764	$39.48	$39.50	$39.50
Purchase #4	$145.70	4.638%	$152.4576	$152.46	$152.45	$152.50
Purchase #5	$232.49	13.566%	$264.0296	$264.03	$264.05	$264.00
Purchase #6	$62.59	4.132%	$65.1762	$65.18	$65.20	$65.20
Purchase #7	$135.57	11.497%	$151.1565	$151.16	$151.15	$151.20
7 purchase totals =	$976.45		$1,075.2335	$1,075.25	$1,075.30	$1,075.40