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	$48.53	13.197%	$54.9345	$54.93	$54.95	$54.90
Purchase #2	$32.77	7.731%	$35.3034	$35.30	$35.30	$35.30
Purchase #3	$173.59	3.867%	$180.3027	$180.30	$180.30	$180.30
Purchase #4	$116.79	13.289%	$132.3102	$132.31	$132.30	$132.30
Purchase #5	$98.62	4.580%	$103.1368	$103.14	$103.15	$103.10
Purchase #6	$86.59	3.543%	$89.6579	$89.66	$89.65	$89.70
Purchase #7	$100.26	7.342%	$107.6211	$107.62	$107.60	$107.60
7 purchase totals =	$657.15		$703.2666	$703.26	$703.25	$703.20