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	$105.87	4.142%	$110.2551	$110.26	$110.25	$110.30
Purchase #2	$152.89	7.498%	$164.3537	$164.35	$164.35	$164.40
Purchase #3	$77.94	5.221%	$82.0092	$82.01	$82.00	$82.00
Purchase #4	$130.86	5.606%	$138.196	$138.20	$138.20	$138.20
Purchase #5	$199.56	9.606%	$218.7297	$218.73	$218.75	$218.70
Purchase #6	$98.45	10.771%	$109.054	$109.05	$109.05	$109.10
Purchase #7	$233.29	13.513%	$264.8145	$264.81	$264.80	$264.80
7 purchase totals =	$998.86		$1,087.4122	$1,087.41	$1,087.40	$1,087.50