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	$185.77	5.784%	$196.5149	$196.51	$196.50	$196.50
Purchase #2	$185.34	6.107%	$196.6587	$196.66	$196.65	$196.70
Purchase #3	$223.94	4.110%	$233.1439	$233.14	$233.15	$233.10
Purchase #4	$78.66	12.427%	$88.4351	$88.44	$88.45	$88.40
Purchase #5	$214.48	13.775%	$244.0246	$244.02	$244.00	$244.00
Purchase #6	$96.36	5.732%	$101.8834	$101.88	$101.90	$101.90
Purchase #7	$21.73	5.513%	$22.928	$22.93	$22.95	$22.90
7 purchase totals =	$1,006.28		$1,083.5886	$1,083.58	$1,083.60	$1,083.50