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	$165.56	10.872%	$183.5597	$183.56	$183.55	$183.60
Purchase #2	$78.72	13.835%	$89.6109	$89.61	$89.60	$89.60
Purchase #3	$235.32	12.355%	$264.3938	$264.39	$264.40	$264.40
Purchase #4	$119.87	5.347%	$126.2794	$126.28	$126.30	$126.30
Purchase #5	$204.44	8.530%	$221.8787	$221.88	$221.90	$221.90
Purchase #6	$238.87	10.761%	$264.5748	$264.57	$264.55	$264.60
Purchase #7	$61.91	8.294%	$67.0448	$67.04	$67.05	$67.00
7 purchase totals =	$1,104.69		$1,217.3421	$1,217.33	$1,217.35	$1,217.40