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	$95.65	12.349%	$107.4618	$107.46	$107.45	$107.50
Purchase #2	$33.38	7.516%	$35.8888	$35.89	$35.90	$35.90
Purchase #3	$73.64	6.520%	$78.4413	$78.44	$78.45	$78.40
Purchase #4	$216.72	13.221%	$245.3726	$245.37	$245.35	$245.40
Purchase #5	$164.80	12.395%	$185.227	$185.23	$185.25	$185.20
Purchase #6	$48.31	7.765%	$52.0613	$52.06	$52.05	$52.10
Purchase #7	$172.32	5.704%	$182.1491	$182.15	$182.15	$182.10
7 purchase totals =	$804.82		$886.6019	$886.60	$886.60	$886.60