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	$109.37	4.809%	$114.6296	$114.63	$114.65	$114.60
Purchase #2	$93.32	13.779%	$106.1786	$106.18	$106.20	$106.20
Purchase #3	$42.91	5.123%	$45.1083	$45.11	$45.10	$45.10
Purchase #4	$133.95	4.161%	$139.5237	$139.52	$139.50	$139.50
Purchase #5	$235.99	6.315%	$250.8928	$250.89	$250.90	$250.90
Purchase #6	$41.26	11.780%	$46.1204	$46.12	$46.10	$46.10
Purchase #7	$93.98	10.685%	$104.0218	$104.02	$104.00	$104.00
7 purchase totals =	$750.78		$806.4752	$806.47	$806.45	$806.40