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	$22.72	11.208%	$25.2665	$25.27	$25.25	$25.30
Purchase #2	$175.46	11.318%	$195.3186	$195.32	$195.30	$195.30
Purchase #3	$51.32	6.121%	$54.4613	$54.46	$54.45	$54.50
Purchase #4	$115.42	7.852%	$124.4828	$124.48	$124.50	$124.50
Purchase #5	$202.51	7.810%	$218.326	$218.33	$218.35	$218.30
Purchase #6	$27.45	6.498%	$29.2337	$29.23	$29.25	$29.20
Purchase #7	$191.95	3.850%	$199.3401	$199.34	$199.35	$199.30
7 purchase totals =	$786.83		$846.4290	$846.43	$846.45	$846.40