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	$162.76	8.338%	$176.3309	$176.33	$176.35	$176.30
Purchase #2	$161.96	6.678%	$172.7757	$172.78	$172.80	$172.80
Purchase #3	$128.54	9.383%	$140.6009	$140.60	$140.60	$140.60
Purchase #4	$58.52	5.501%	$61.7392	$61.74	$61.75	$61.70
Purchase #5	$220.98	12.806%	$249.2787	$249.28	$249.30	$249.30
Purchase #6	$166.92	4.475%	$174.3897	$174.39	$174.40	$174.40
Purchase #7	$198.92	11.197%	$221.1931	$221.19	$221.20	$221.20
7 purchase totals =	$1,098.60		$1,196.3082	$1,196.31	$1,196.40	$1,196.30