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	$215.75	12.449%	$242.6087	$242.61	$242.60	$242.60
Purchase #2	$174.94	6.463%	$186.2464	$186.25	$186.25	$186.20
Purchase #3	$105.36	4.239%	$109.8262	$109.83	$109.85	$109.80
Purchase #4	$28.26	12.228%	$31.7156	$31.72	$31.70	$31.70
Purchase #5	$175.91	3.593%	$182.2304	$182.23	$182.25	$182.20
Purchase #6	$187.53	5.839%	$198.4799	$198.48	$198.50	$198.50
Purchase #7	$138.56	10.203%	$152.6973	$152.70	$152.70	$152.70
7 purchase totals =	$1,026.31		$1,103.8045	$1,103.82	$1,103.85	$1,103.70