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	$132.38	11.135%	$147.1205	$147.12	$147.10	$147.10
Purchase #2	$83.28	3.512%	$86.2048	$86.20	$86.20	$86.20
Purchase #3	$210.33	5.712%	$222.344	$222.34	$222.35	$222.30
Purchase #4	$184.36	12.201%	$206.8538	$206.85	$206.85	$206.90
Purchase #5	$239.35	11.578%	$267.0619	$267.06	$267.05	$267.10
Purchase #6	$151.41	13.870%	$172.4106	$172.41	$172.40	$172.40
Purchase #7	$69.72	12.375%	$78.3479	$78.35	$78.35	$78.30
7 purchase totals =	$1,070.83		$1,180.3435	$1,180.33	$1,180.30	$1,180.30