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	$188.62	12.555%	$212.3012	$212.30	$212.30	$212.30
Purchase #2	$216.55	3.435%	$223.9885	$223.99	$224.00	$224.00
Purchase #3	$202.79	10.350%	$223.7788	$223.78	$223.80	$223.80
Purchase #4	$249.86	5.851%	$264.4793	$264.48	$264.50	$264.50
Purchase #5	$160.65	5.562%	$169.5854	$169.59	$169.60	$169.60
Purchase #6	$80.28	12.538%	$90.3455	$90.35	$90.35	$90.30
Purchase #7	$202.86	6.801%	$216.6565	$216.66	$216.65	$216.70
7 purchase totals =	$1,301.61		$1,401.1352	$1,401.15	$1,401.20	$1,401.20