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	$156.74	11.272%	$174.4077	$174.41	$174.40	$174.40
Purchase #2	$191.83	12.644%	$216.085	$216.09	$216.10	$216.10
Purchase #3	$246.70	7.342%	$264.8127	$264.81	$264.80	$264.80
Purchase #4	$177.32	6.193%	$188.3014	$188.30	$188.30	$188.30
Purchase #5	$42.36	9.368%	$46.3283	$46.33	$46.35	$46.30
Purchase #6	$13.43	12.143%	$15.0608	$15.06	$15.05	$15.10
Purchase #7	$160.94	13.274%	$182.3032	$182.30	$182.30	$182.30
7 purchase totals =	$989.32		$1,087.2991	$1,087.30	$1,087.30	$1,087.30