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	$67.39	7.265%	$72.2859	$72.29	$72.30	$72.30
Purchase #2	$159.43	9.398%	$174.4132	$174.41	$174.40	$174.40
Purchase #3	$169.42	7.559%	$182.2265	$182.23	$182.25	$182.20
Purchase #4	$78.72	12.857%	$88.841	$88.84	$88.85	$88.80
Purchase #5	$195.74	9.118%	$213.5876	$213.59	$213.60	$213.60
Purchase #6	$160.47	3.823%	$166.6048	$166.60	$166.60	$166.60
Purchase #7	$132.28	13.702%	$150.405	$150.41	$150.40	$150.40
7 purchase totals =	$963.45		$1,048.3640	$1,048.37	$1,048.40	$1,048.30