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	$94.77	4.586%	$99.1162	$99.12	$99.10	$99.10
Purchase #2	$100.44	3.436%	$103.8911	$103.89	$103.90	$103.90
Purchase #3	$245.60	9.484%	$268.8927	$268.89	$268.90	$268.90
Purchase #4	$35.38	3.233%	$36.5238	$36.52	$36.50	$36.50
Purchase #5	$12.53	4.204%	$13.0568	$13.06	$13.05	$13.10
Purchase #6	$145.98	10.834%	$161.7955	$161.80	$161.80	$161.80
Purchase #7	$68.47	4.114%	$71.2869	$71.29	$71.30	$71.30
7 purchase totals =	$703.17		$754.5630	$754.57	$754.55	$754.60