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	$91.31	4.293%	$95.2299	$95.23	$95.25	$95.20
Purchase #2	$50.53	8.508%	$54.8291	$54.83	$54.85	$54.80
Purchase #3	$128.58	4.127%	$133.8865	$133.89	$133.90	$133.90
Purchase #4	$35.77	7.216%	$38.3512	$38.35	$38.35	$38.40
Purchase #5	$78.98	5.724%	$83.5008	$83.50	$83.50	$83.50
Purchase #6	$55.79	7.220%	$59.818	$59.82	$59.80	$59.80
Purchase #7	$53.50	11.276%	$59.5327	$59.53	$59.55	$59.50
7 purchase totals =	$494.46		$525.1482	$525.15	$525.20	$525.10