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	$153.48	10.328%	$169.3314	$169.33	$169.35	$169.30
Purchase #2	$64.47	4.823%	$67.5794	$67.58	$67.60	$67.60
Purchase #3	$242.65	11.715%	$271.0764	$271.08	$271.10	$271.10
Purchase #4	$39.61	13.564%	$44.9827	$44.98	$45.00	$45.00
Purchase #5	$94.71	5.314%	$99.7429	$99.74	$99.75	$99.70
Purchase #6	$197.36	11.288%	$219.638	$219.64	$219.65	$219.60
Purchase #7	$173.55	13.155%	$196.3805	$196.38	$196.40	$196.40
7 purchase totals =	$965.83		$1,068.7313	$1,068.73	$1,068.85	$1,068.70