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	$68.64	7.282%	$73.6384	$73.64	$73.65	$73.60
Purchase #2	$210.44	11.820%	$235.314	$235.31	$235.30	$235.30
Purchase #3	$127.29	3.396%	$131.6128	$131.61	$131.60	$131.60
Purchase #4	$157.42	7.689%	$169.524	$169.52	$169.50	$169.50
Purchase #5	$48.37	13.499%	$54.8995	$54.90	$54.90	$54.90
Purchase #6	$127.25	11.593%	$142.0021	$142.00	$142.00	$142.00
Purchase #7	$182.54	8.565%	$198.1746	$198.17	$198.15	$198.20
7 purchase totals =	$921.95		$1,005.1654	$1,005.15	$1,005.10	$1,005.10