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	$94.41	7.632%	$101.6154	$101.62	$101.60	$101.60
Purchase #2	$180.80	5.784%	$191.2575	$191.26	$191.25	$191.30
Purchase #3	$69.73	12.749%	$78.6199	$78.62	$78.60	$78.60
Purchase #4	$136.32	11.724%	$152.3022	$152.30	$152.30	$152.30
Purchase #5	$167.74	9.833%	$184.2339	$184.23	$184.25	$184.20
Purchase #6	$131.33	8.237%	$142.1477	$142.15	$142.15	$142.10
Purchase #7	$169.66	13.128%	$191.933	$191.93	$191.95	$191.90
7 purchase totals =	$949.99		$1,042.1096	$1,042.11	$1,042.10	$1,042.00