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	$65.73	5.277%	$69.1986	$69.20	$69.20	$69.20
Purchase #2	$20.48	4.356%	$21.3721	$21.37	$21.35	$21.40
Purchase #3	$30.27	6.745%	$32.3117	$32.31	$32.30	$32.30
Purchase #4	$250.39	10.286%	$276.1451	$276.15	$276.15	$276.10
Purchase #5	$99.67	11.510%	$111.142	$111.14	$111.15	$111.10
Purchase #6	$143.67	3.234%	$148.3163	$148.32	$148.30	$148.30
Purchase #7	$124.92	3.479%	$129.266	$129.27	$129.25	$129.30
7 purchase totals =	$735.13		$787.7518	$787.76	$787.70	$787.70