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	$97.95	9.553%	$107.3072	$107.31	$107.30	$107.30
Purchase #2	$201.37	12.810%	$227.1655	$227.17	$227.15	$227.20
Purchase #3	$43.77	6.464%	$46.5993	$46.60	$46.60	$46.60
Purchase #4	$42.94	6.519%	$45.7393	$45.74	$45.75	$45.70
Purchase #5	$225.40	11.314%	$250.9018	$250.90	$250.90	$250.90
Purchase #6	$227.39	6.660%	$242.5342	$242.53	$242.55	$242.50
Purchase #7	$215.56	3.586%	$223.29	$223.29	$223.30	$223.30
7 purchase totals =	$1,054.38		$1,143.5373	$1,143.54	$1,143.55	$1,143.50