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	$219.25	6.437%	$233.3631	$233.36	$233.35	$233.40
Purchase #2	$72.90	5.658%	$77.0247	$77.02	$77.00	$77.00
Purchase #3	$86.88	3.480%	$89.9034	$89.90	$89.90	$89.90
Purchase #4	$67.42	11.719%	$75.3209	$75.32	$75.30	$75.30
Purchase #5	$179.37	9.409%	$196.2469	$196.25	$196.25	$196.20
Purchase #6	$104.41	6.479%	$111.1747	$111.17	$111.15	$111.20
Purchase #7	$18.71	12.839%	$21.1122	$21.11	$21.10	$21.10
7 purchase totals =	$748.94		$804.1459	$804.13	$804.05	$804.10