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	$83.87	5.615%	$88.5793	$88.58	$88.60	$88.60
Purchase #2	$50.90	5.658%	$53.7799	$53.78	$53.80	$53.80
Purchase #3	$228.30	4.748%	$239.1397	$239.14	$239.15	$239.10
Purchase #4	$106.80	8.530%	$115.91	$115.91	$115.90	$115.90
Purchase #5	$164.32	12.691%	$185.1739	$185.17	$185.15	$185.20
Purchase #6	$24.60	13.224%	$27.8531	$27.85	$27.85	$27.90
Purchase #7	$53.85	3.597%	$55.787	$55.79	$55.80	$55.80
7 purchase totals =	$712.64		$766.2229	$766.22	$766.25	$766.30