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	$100.45	3.478%	$103.9437	$103.94	$103.95	$103.90
Purchase #2	$105.34	11.370%	$117.3172	$117.32	$117.30	$117.30
Purchase #3	$215.89	12.712%	$243.3339	$243.33	$243.35	$243.30
Purchase #4	$204.72	11.412%	$228.0826	$228.08	$228.10	$228.10
Purchase #5	$249.30	10.385%	$275.1898	$275.19	$275.20	$275.20
Purchase #6	$218.48	5.838%	$231.2349	$231.23	$231.25	$231.20
Purchase #7	$9.80	7.253%	$10.5108	$10.51	$10.50	$10.50
7 purchase totals =	$1,103.98		$1,209.6129	$1,209.60	$1,209.65	$1,209.50