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	$61.88	11.776%	$69.167	$69.17	$69.15	$69.20
Purchase #2	$157.36	9.153%	$171.7632	$171.76	$171.75	$171.80
Purchase #3	$248.93	11.792%	$278.2838	$278.28	$278.30	$278.30
Purchase #4	$127.28	10.830%	$141.0644	$141.06	$141.05	$141.10
Purchase #5	$133.69	8.156%	$144.5938	$144.59	$144.60	$144.60
Purchase #6	$243.59	6.549%	$259.5427	$259.54	$259.55	$259.50
Purchase #7	$77.47	7.346%	$83.1609	$83.16	$83.15	$83.20
7 purchase totals =	$1,050.20		$1,147.5758	$1,147.56	$1,147.55	$1,147.70