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	$182.97	6.727%	$195.2784	$195.28	$195.30	$195.30
Purchase #2	$74.33	8.815%	$80.8822	$80.88	$80.90	$80.90
Purchase #3	$161.72	6.806%	$172.7267	$172.73	$172.75	$172.70
Purchase #4	$83.31	12.306%	$93.5621	$93.56	$93.55	$93.60
Purchase #5	$171.28	6.189%	$181.8805	$181.88	$181.90	$181.90
Purchase #6	$94.52	11.663%	$105.5439	$105.54	$105.55	$105.50
Purchase #7	$68.86	4.404%	$71.8926	$71.89	$71.90	$71.90
7 purchase totals =	$836.99		$901.7664	$901.76	$901.85	$901.80