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	$188.37	12.795%	$212.4719	$212.47	$212.45	$212.50
Purchase #2	$182.25	3.452%	$188.5413	$188.54	$188.55	$188.50
Purchase #3	$98.93	9.859%	$108.6835	$108.68	$108.70	$108.70
Purchase #4	$82.77	9.651%	$90.7581	$90.76	$90.75	$90.80
Purchase #5	$85.31	9.665%	$93.5552	$93.56	$93.55	$93.60
Purchase #6	$32.89	7.645%	$35.4044	$35.40	$35.40	$35.40
Purchase #7	$157.60	3.262%	$162.7409	$162.74	$162.75	$162.70
7 purchase totals =	$828.12		$892.1553	$892.15	$892.15	$892.20