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	$119.73	7.229%	$128.3853	$128.39	$128.40	$128.40
Purchase #2	$73.61	12.817%	$83.0446	$83.04	$83.05	$83.00
Purchase #3	$121.44	5.596%	$128.2358	$128.24	$128.25	$128.20
Purchase #4	$108.97	7.138%	$116.7483	$116.75	$116.75	$116.70
Purchase #5	$193.49	11.834%	$216.3876	$216.39	$216.40	$216.40
Purchase #6	$217.28	11.761%	$242.8343	$242.83	$242.85	$242.80
Purchase #7	$92.37	9.744%	$101.3705	$101.37	$101.35	$101.40
7 purchase totals =	$926.89		$1,017.0064	$1,017.01	$1,017.05	$1,016.90