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	$130.43	5.600%	$137.7341	$137.73	$137.75	$137.70
Purchase #2	$174.47	4.603%	$182.5009	$182.50	$182.50	$182.50
Purchase #3	$165.62	3.688%	$171.7281	$171.73	$171.75	$171.70
Purchase #4	$136.75	11.381%	$152.3135	$152.31	$152.30	$152.30
Purchase #5	$154.25	5.108%	$162.1291	$162.13	$162.15	$162.10
Purchase #6	$244.53	11.721%	$273.1914	$273.19	$273.20	$273.20
Purchase #7	$169.54	9.470%	$185.5954	$185.60	$185.60	$185.60
7 purchase totals =	$1,175.59		$1,265.1925	$1,265.19	$1,265.25	$1,265.10