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	$33.33	11.791%	$37.2599	$37.26	$37.25	$37.30
Purchase #2	$213.73	7.566%	$229.9008	$229.90	$229.90	$229.90
Purchase #3	$192.73	8.803%	$209.696	$209.70	$209.70	$209.70
Purchase #4	$193.79	7.655%	$208.6246	$208.62	$208.60	$208.60
Purchase #5	$185.54	3.359%	$191.7723	$191.77	$191.75	$191.80
Purchase #6	$73.28	7.418%	$78.7159	$78.72	$78.70	$78.70
Purchase #7	$147.32	8.630%	$160.0337	$160.03	$160.05	$160.00
7 purchase totals =	$1,039.72		$1,116.0032	$1,116.00	$1,115.95	$1,116.00