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	$172.72	13.573%	$196.1633	$196.16	$196.15	$196.20
Purchase #2	$19.96	3.872%	$20.7329	$20.73	$20.75	$20.70
Purchase #3	$240.71	11.744%	$268.979	$268.98	$269.00	$269.00
Purchase #4	$54.31	4.724%	$56.8756	$56.88	$56.90	$56.90
Purchase #5	$204.98	5.568%	$216.3933	$216.39	$216.40	$216.40
Purchase #6	$238.79	5.394%	$251.6703	$251.67	$251.65	$251.70
Purchase #7	$67.53	6.836%	$72.1464	$72.15	$72.15	$72.10
7 purchase totals =	$999.00		$1,082.9608	$1,082.96	$1,083.00	$1,083.00