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	$98.30	9.735%	$107.8695	$107.87	$107.85	$107.90
Purchase #2	$236.93	11.522%	$264.2291	$264.23	$264.25	$264.20
Purchase #3	$16.39	12.630%	$18.4601	$18.46	$18.45	$18.50
Purchase #4	$249.72	8.824%	$271.7553	$271.76	$271.75	$271.80
Purchase #5	$247.87	11.230%	$275.7058	$275.71	$275.70	$275.70
Purchase #6	$175.83	8.842%	$191.3769	$191.38	$191.40	$191.40
Purchase #7	$241.29	5.674%	$254.9808	$254.98	$255.00	$255.00
7 purchase totals =	$1,266.33		$1,384.3775	$1,384.39	$1,384.40	$1,384.50