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	$221.60	12.315%	$248.89	$248.89	$248.90	$248.90
Purchase #2	$238.43	13.689%	$271.0687	$271.07	$271.05	$271.10
Purchase #3	$148.94	8.355%	$161.3839	$161.38	$161.40	$161.40
Purchase #4	$142.54	3.411%	$147.402	$147.40	$147.40	$147.40
Purchase #5	$47.53	12.349%	$53.3995	$53.40	$53.40	$53.40
Purchase #6	$189.44	13.574%	$215.1546	$215.15	$215.15	$215.20
Purchase #7	$5.86	10.640%	$6.4835	$6.48	$6.50	$6.50
7 purchase totals =	$994.34		$1,103.7822	$1,103.77	$1,103.80	$1,103.90