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	$149.52	13.403%	$169.5602	$169.56	$169.55	$169.60
Purchase #2	$219.63	6.543%	$234.0004	$234.00	$234.00	$234.00
Purchase #3	$59.35	4.731%	$62.1578	$62.16	$62.15	$62.20
Purchase #4	$180.55	8.834%	$196.4998	$196.50	$196.50	$196.50
Purchase #5	$10.48	3.754%	$10.8734	$10.87	$10.85	$10.90
Purchase #6	$29.82	12.464%	$33.5368	$33.54	$33.55	$33.50
Purchase #7	$55.76	7.553%	$59.9716	$59.97	$59.95	$60.00
7 purchase totals =	$705.11		$766.6000	$766.60	$766.55	$766.70