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	$208.83	9.119%	$227.8732	$227.87	$227.85	$227.90
Purchase #2	$36.28	11.123%	$40.3154	$40.32	$40.30	$40.30
Purchase #3	$54.59	9.476%	$59.7629	$59.76	$59.75	$59.80
Purchase #4	$106.51	4.811%	$111.6342	$111.63	$111.65	$111.60
Purchase #5	$139.54	4.173%	$145.363	$145.36	$145.35	$145.40
Purchase #6	$123.61	4.428%	$129.0835	$129.08	$129.10	$129.10
Purchase #7	$236.96	8.582%	$257.2959	$257.30	$257.30	$257.30
7 purchase totals =	$906.32		$971.3281	$971.32	$971.30	$971.40