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	$153.96	11.754%	$172.0565	$172.06	$172.05	$172.10
Purchase #2	$138.27	10.632%	$152.9709	$152.97	$152.95	$153.00
Purchase #3	$10.50	4.173%	$10.9382	$10.94	$10.95	$10.90
Purchase #4	$64.85	9.253%	$70.8506	$70.85	$70.85	$70.90
Purchase #5	$41.47	9.484%	$45.403	$45.40	$45.40	$45.40
Purchase #6	$25.57	9.501%	$27.9994	$28.00	$28.00	$28.00
Purchase #7	$162.52	13.843%	$185.0176	$185.02	$185.00	$185.00
7 purchase totals =	$597.14		$665.2362	$665.24	$665.20	$665.30