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	$215.83	11.814%	$241.3282	$241.33	$241.35	$241.30
Purchase #2	$35.91	13.543%	$40.7733	$40.77	$40.75	$40.80
Purchase #3	$85.51	11.730%	$95.5403	$95.54	$95.55	$95.50
Purchase #4	$28.40	11.864%	$31.7694	$31.77	$31.75	$31.80
Purchase #5	$87.59	11.550%	$97.7066	$97.71	$97.70	$97.70
Purchase #6	$162.65	4.291%	$169.6293	$169.63	$169.65	$169.60
Purchase #7	$48.83	4.380%	$50.9688	$50.97	$50.95	$51.00
7 purchase totals =	$664.72		$727.7159	$727.72	$727.70	$727.70