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	$40.67	5.607%	$42.9504	$42.95	$42.95	$43.00
Purchase #2	$159.98	11.435%	$178.2737	$178.27	$178.25	$178.30
Purchase #3	$154.59	12.235%	$173.5041	$173.50	$173.50	$173.50
Purchase #4	$42.44	7.660%	$45.6909	$45.69	$45.70	$45.70
Purchase #5	$96.52	5.594%	$101.9193	$101.92	$101.90	$101.90
Purchase #6	$181.41	4.221%	$189.0673	$189.07	$189.05	$189.10
Purchase #7	$137.70	13.221%	$155.9053	$155.91	$155.90	$155.90
7 purchase totals =	$813.31		$887.3110	$887.31	$887.25	$887.40