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	$109.33	6.187%	$116.0942	$116.09	$116.10	$116.10
Purchase #2	$98.75	11.309%	$109.9176	$109.92	$109.90	$109.90
Purchase #3	$134.40	13.644%	$152.7375	$152.74	$152.75	$152.70
Purchase #4	$54.65	11.611%	$60.9954	$61.00	$61.00	$61.00
Purchase #5	$148.77	4.343%	$155.2311	$155.23	$155.25	$155.20
Purchase #6	$138.71	5.820%	$146.7829	$146.78	$146.80	$146.80
Purchase #7	$243.47	7.672%	$262.149	$262.15	$262.15	$262.10
7 purchase totals =	$928.08		$1,003.9077	$1,003.91	$1,003.95	$1,003.80