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	$71.46	7.238%	$76.6323	$76.63	$76.65	$76.60
Purchase #2	$82.75	8.250%	$89.5769	$89.58	$89.60	$89.60
Purchase #3	$172.54	9.816%	$189.4765	$189.48	$189.50	$189.50
Purchase #4	$220.52	5.803%	$233.3168	$233.32	$233.30	$233.30
Purchase #5	$228.42	4.354%	$238.3654	$238.37	$238.35	$238.40
Purchase #6	$198.65	11.819%	$222.1284	$222.13	$222.15	$222.10
Purchase #7	$170.87	13.574%	$194.0639	$194.06	$194.05	$194.10
7 purchase totals =	$1,145.21		$1,243.5602	$1,243.57	$1,243.60	$1,243.60