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	$148.37	10.607%	$164.1076	$164.11	$164.10	$164.10
Purchase #2	$34.91	5.640%	$36.8789	$36.88	$36.90	$36.90
Purchase #3	$100.78	12.850%	$113.7302	$113.73	$113.75	$113.70
Purchase #4	$67.67	12.707%	$76.2688	$76.27	$76.25	$76.30
Purchase #5	$12.65	12.767%	$14.265	$14.27	$14.25	$14.30
Purchase #6	$40.76	6.378%	$43.3597	$43.36	$43.35	$43.40
Purchase #7	$33.35	5.789%	$35.2806	$35.28	$35.30	$35.30
7 purchase totals =	$438.49		$483.8908	$483.90	$483.90	$484.00