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	$71.98	3.119%	$74.2251	$74.23	$74.25	$74.20
Purchase #2	$28.50	9.869%	$31.3127	$31.31	$31.30	$31.30
Purchase #3	$169.34	7.244%	$181.607	$181.61	$181.60	$181.60
Purchase #4	$90.62	3.264%	$93.5778	$93.58	$93.60	$93.60
Purchase #5	$84.98	5.196%	$89.3956	$89.40	$89.40	$89.40
Purchase #6	$57.68	8.430%	$62.5424	$62.54	$62.55	$62.50
Purchase #7	$230.86	11.136%	$256.5686	$256.57	$256.55	$256.60
7 purchase totals =	$733.96		$789.2292	$789.24	$789.25	$789.20