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	$173.47	8.310%	$187.8854	$187.89	$187.90	$187.90
Purchase #2	$191.40	3.481%	$198.0626	$198.06	$198.05	$198.10
Purchase #3	$76.27	3.249%	$78.748	$78.75	$78.75	$78.70
Purchase #4	$9.40	7.764%	$10.1298	$10.13	$10.15	$10.10
Purchase #5	$80.26	11.338%	$89.3599	$89.36	$89.35	$89.40
Purchase #6	$100.54	7.585%	$108.166	$108.17	$108.15	$108.20
Purchase #7	$224.41	3.105%	$231.3779	$231.38	$231.40	$231.40
7 purchase totals =	$855.75		$903.7296	$903.74	$903.75	$903.80