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	$173.30	8.614%	$188.2281	$188.23	$188.25	$188.20
Purchase #2	$67.28	13.863%	$76.607	$76.61	$76.60	$76.60
Purchase #3	$205.86	10.632%	$227.747	$227.75	$227.75	$227.70
Purchase #4	$157.92	4.637%	$165.2428	$165.24	$165.25	$165.20
Purchase #5	$203.48	12.710%	$229.3423	$229.34	$229.35	$229.30
Purchase #6	$191.81	11.220%	$213.3311	$213.33	$213.35	$213.30
Purchase #7	$9.87	13.424%	$11.1949	$11.19	$11.20	$11.20
7 purchase totals =	$1,009.52		$1,111.6932	$1,111.69	$1,111.75	$1,111.50