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	$141.48	8.133%	$152.9866	$152.99	$153.00	$153.00
Purchase #2	$111.93	5.631%	$118.2328	$118.23	$118.25	$118.20
Purchase #3	$139.83	3.191%	$144.292	$144.29	$144.30	$144.30
Purchase #4	$30.78	5.709%	$32.5372	$32.54	$32.55	$32.50
Purchase #5	$141.76	3.670%	$146.9626	$146.96	$146.95	$147.00
Purchase #6	$126.86	12.631%	$142.8837	$142.88	$142.90	$142.90
Purchase #7	$161.36	5.311%	$169.9298	$169.93	$169.95	$169.90
7 purchase totals =	$854.00		$907.8247	$907.82	$907.90	$907.80