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	$221.43	7.727%	$238.5399	$238.54	$238.55	$238.50
Purchase #2	$33.89	9.626%	$37.1523	$37.15	$37.15	$37.20
Purchase #3	$182.98	11.856%	$204.6741	$204.67	$204.65	$204.70
Purchase #4	$211.83	3.663%	$219.5893	$219.59	$219.60	$219.60
Purchase #5	$162.29	4.304%	$169.275	$169.28	$169.30	$169.30
Purchase #6	$35.45	9.345%	$38.7628	$38.76	$38.75	$38.80
Purchase #7	$63.37	3.408%	$65.5296	$65.53	$65.55	$65.50
7 purchase totals =	$911.24		$973.5230	$973.52	$973.55	$973.60