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	$196.37	7.715%	$211.5199	$211.52	$211.50	$211.50
Purchase #2	$99.37	3.348%	$102.6969	$102.70	$102.70	$102.70
Purchase #3	$21.68	6.627%	$23.1167	$23.12	$23.10	$23.10
Purchase #4	$149.84	3.550%	$155.1593	$155.16	$155.15	$155.20
Purchase #5	$94.35	6.527%	$100.5082	$100.51	$100.50	$100.50
Purchase #6	$147.47	11.432%	$164.3288	$164.33	$164.35	$164.30
Purchase #7	$79.89	11.619%	$89.1724	$89.17	$89.15	$89.20
7 purchase totals =	$788.97		$846.5022	$846.51	$846.45	$846.50