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	$219.69	4.412%	$229.3827	$229.38	$229.40	$229.40
Purchase #2	$164.77	12.698%	$185.6925	$185.69	$185.70	$185.70
Purchase #3	$45.33	6.842%	$48.4315	$48.43	$48.45	$48.40
Purchase #4	$223.63	7.688%	$240.8227	$240.82	$240.80	$240.80
Purchase #5	$29.31	8.323%	$31.7495	$31.75	$31.75	$31.70
Purchase #6	$237.76	9.118%	$259.439	$259.44	$259.45	$259.40
Purchase #7	$31.42	13.790%	$35.7528	$35.75	$35.75	$35.80
7 purchase totals =	$951.91		$1,031.2707	$1,031.26	$1,031.30	$1,031.20