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	$191.50	3.399%	$198.0091	$198.01	$198.00	$198.00
Purchase #2	$132.27	7.679%	$142.427	$142.43	$142.45	$142.40
Purchase #3	$186.94	5.287%	$196.8235	$196.82	$196.80	$196.80
Purchase #4	$205.73	4.581%	$215.1545	$215.15	$215.15	$215.20
Purchase #5	$61.74	11.521%	$68.8531	$68.85	$68.85	$68.90
Purchase #6	$237.87	3.327%	$245.7839	$245.78	$245.80	$245.80
Purchase #7	$197.89	5.732%	$209.2331	$209.23	$209.25	$209.20
7 purchase totals =	$1,213.94		$1,276.2842	$1,276.27	$1,276.30	$1,276.30