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	$73.68	6.695%	$78.6129	$78.61	$78.60	$78.60
Purchase #2	$161.53	4.689%	$169.1041	$169.10	$169.10	$169.10
Purchase #3	$109.62	3.559%	$113.5214	$113.52	$113.50	$113.50
Purchase #4	$222.31	6.304%	$236.3244	$236.32	$236.30	$236.30
Purchase #5	$12.79	8.112%	$13.8275	$13.83	$13.85	$13.80
Purchase #6	$106.67	4.369%	$111.3304	$111.33	$111.35	$111.30
Purchase #7	$206.28	3.574%	$213.6524	$213.65	$213.65	$213.70
7 purchase totals =	$892.88		$936.3731	$936.36	$936.35	$936.30