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	$26.59	10.305%	$29.3301	$29.33	$29.35	$29.30
Purchase #2	$72.97	11.199%	$81.1419	$81.14	$81.15	$81.10
Purchase #3	$41.69	8.672%	$45.3054	$45.31	$45.30	$45.30
Purchase #4	$187.59	9.803%	$205.9794	$205.98	$206.00	$206.00
Purchase #5	$247.44	3.316%	$255.6451	$255.65	$255.65	$255.60
Purchase #6	$178.50	11.328%	$198.7205	$198.72	$198.70	$198.70
Purchase #7	$142.29	7.192%	$152.5235	$152.52	$152.50	$152.50
7 purchase totals =	$897.07		$968.6459	$968.65	$968.65	$968.50