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	$187.90	4.607%	$196.5566	$196.56	$196.55	$196.60
Purchase #2	$234.30	9.743%	$257.1278	$257.13	$257.15	$257.10
Purchase #3	$23.68	13.734%	$26.9322	$26.93	$26.95	$26.90
Purchase #4	$198.58	13.419%	$225.2275	$225.23	$225.25	$225.20
Purchase #5	$162.74	5.111%	$171.0576	$171.06	$171.05	$171.10
Purchase #6	$70.25	11.701%	$78.47	$78.47	$78.45	$78.50
Purchase #7	$106.72	10.572%	$118.0024	$118.00	$118.00	$118.00
7 purchase totals =	$984.17		$1,073.3741	$1,073.38	$1,073.40	$1,073.40