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	$211.88	5.504%	$223.5419	$223.54	$223.55	$223.50
Purchase #2	$86.67	11.832%	$96.9248	$96.92	$96.90	$96.90
Purchase #3	$6.62	13.815%	$7.5346	$7.53	$7.55	$7.50
Purchase #4	$32.97	7.520%	$35.4493	$35.45	$35.45	$35.40
Purchase #5	$38.46	10.735%	$42.5887	$42.59	$42.60	$42.60
Purchase #6	$109.56	13.439%	$124.2838	$124.28	$124.30	$124.30
Purchase #7	$193.39	3.178%	$199.5359	$199.54	$199.55	$199.50
7 purchase totals =	$679.55		$729.8590	$729.85	$729.90	$729.70