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	$68.54	8.204%	$74.163	$74.16	$74.15	$74.20
Purchase #2	$142.90	9.831%	$156.9485	$156.95	$156.95	$156.90
Purchase #3	$59.43	11.189%	$66.0796	$66.08	$66.10	$66.10
Purchase #4	$50.89	6.402%	$54.148	$54.15	$54.15	$54.10
Purchase #5	$144.55	11.174%	$160.702	$160.70	$160.70	$160.70
Purchase #6	$64.55	4.596%	$67.5167	$67.52	$67.50	$67.50
Purchase #7	$245.65	7.722%	$264.6191	$264.62	$264.60	$264.60
7 purchase totals =	$776.51		$844.1769	$844.18	$844.15	$844.10