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	$68.89	10.762%	$76.3039	$76.30	$76.30	$76.30
Purchase #2	$92.51	11.839%	$103.4623	$103.46	$103.45	$103.50
Purchase #3	$249.84	12.610%	$281.3448	$281.34	$281.35	$281.30
Purchase #4	$139.78	5.672%	$147.7083	$147.71	$147.70	$147.70
Purchase #5	$240.69	6.647%	$256.6887	$256.69	$256.70	$256.70
Purchase #6	$93.87	11.132%	$104.3196	$104.32	$104.30	$104.30
Purchase #7	$242.54	10.619%	$268.2953	$268.30	$268.30	$268.30
7 purchase totals =	$1,128.12		$1,238.1229	$1,238.12	$1,238.10	$1,238.10