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	$179.44	3.275%	$185.3167	$185.32	$185.30	$185.30
Purchase #2	$220.59	4.350%	$230.1857	$230.19	$230.20	$230.20
Purchase #3	$148.27	11.362%	$165.1164	$165.12	$165.10	$165.10
Purchase #4	$34.29	10.119%	$37.7598	$37.76	$37.75	$37.80
Purchase #5	$48.99	10.709%	$54.2363	$54.24	$54.25	$54.20
Purchase #6	$196.78	12.527%	$221.4306	$221.43	$221.45	$221.40
Purchase #7	$102.98	3.692%	$106.782	$106.78	$106.80	$106.80
7 purchase totals =	$931.34		$1,000.8275	$1,000.84	$1,000.85	$1,000.80