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	$157.67	4.869%	$165.347	$165.35	$165.35	$165.30
Purchase #2	$232.54	13.471%	$263.8655	$263.87	$263.85	$263.90
Purchase #3	$98.65	4.246%	$102.8387	$102.84	$102.85	$102.80
Purchase #4	$176.86	6.816%	$188.9148	$188.91	$188.90	$188.90
Purchase #5	$50.37	3.373%	$52.069	$52.07	$52.05	$52.10
Purchase #6	$61.80	9.407%	$67.6135	$67.61	$67.60	$67.60
Purchase #7	$142.77	7.822%	$153.9375	$153.94	$153.95	$153.90
7 purchase totals =	$920.66		$994.5860	$994.59	$994.55	$994.50