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	$108.82	7.548%	$117.0337	$117.03	$117.05	$117.00
Purchase #2	$243.50	10.425%	$268.8849	$268.88	$268.90	$268.90
Purchase #3	$42.95	5.395%	$45.2672	$45.27	$45.25	$45.30
Purchase #4	$133.40	13.192%	$150.9981	$151.00	$151.00	$151.00
Purchase #5	$79.82	12.285%	$89.6259	$89.63	$89.65	$89.60
Purchase #6	$159.61	3.633%	$165.4086	$165.41	$165.40	$165.40
Purchase #7	$73.30	4.417%	$76.5377	$76.54	$76.55	$76.50
7 purchase totals =	$841.40		$913.7561	$913.76	$913.80	$913.70