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	$221.98	13.449%	$251.8341	$251.83	$251.85	$251.80
Purchase #2	$73.67	11.311%	$82.0028	$82.00	$82.00	$82.00
Purchase #3	$196.38	4.154%	$204.5376	$204.54	$204.55	$204.50
Purchase #4	$111.64	6.423%	$118.8106	$118.81	$118.80	$118.80
Purchase #5	$151.52	11.269%	$168.5948	$168.59	$168.60	$168.60
Purchase #6	$124.75	13.166%	$141.1746	$141.17	$141.15	$141.20
Purchase #7	$194.39	6.123%	$206.2925	$206.29	$206.30	$206.30
7 purchase totals =	$1,074.33		$1,173.2470	$1,173.23	$1,173.25	$1,173.20