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	$97.38	11.157%	$108.2447	$108.24	$108.25	$108.20
Purchase #2	$225.28	9.696%	$247.1231	$247.12	$247.10	$247.10
Purchase #3	$208.70	11.714%	$233.1471	$233.15	$233.15	$233.10
Purchase #4	$209.72	8.203%	$226.9233	$226.92	$226.90	$226.90
Purchase #5	$24.41	13.606%	$27.7312	$27.73	$27.75	$27.70
Purchase #6	$124.52	6.130%	$132.1531	$132.15	$132.15	$132.20
Purchase #7	$178.37	10.121%	$196.4228	$196.42	$196.40	$196.40
7 purchase totals =	$1,068.38		$1,171.7453	$1,171.73	$1,171.70	$1,171.60