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	$77.72	11.644%	$86.7697	$86.77	$86.75	$86.80
Purchase #2	$99.53	6.849%	$106.3468	$106.35	$106.35	$106.30
Purchase #3	$145.81	5.795%	$154.2597	$154.26	$154.25	$154.30
Purchase #4	$56.96	8.728%	$61.9315	$61.93	$61.95	$61.90
Purchase #5	$198.27	5.111%	$208.4036	$208.40	$208.40	$208.40
Purchase #6	$96.39	9.456%	$105.5046	$105.50	$105.50	$105.50
Purchase #7	$144.88	13.745%	$164.7938	$164.79	$164.80	$164.80
7 purchase totals =	$819.56		$888.0097	$888.00	$888.00	$888.00