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	$67.86	7.415%	$72.8918	$72.89	$72.90	$72.90
Purchase #2	$120.95	10.380%	$133.5046	$133.50	$133.50	$133.50
Purchase #3	$19.88	8.681%	$21.6058	$21.61	$21.60	$21.60
Purchase #4	$130.75	10.239%	$144.1375	$144.14	$144.15	$144.10
Purchase #5	$179.47	5.720%	$189.7357	$189.74	$189.75	$189.70
Purchase #6	$135.72	4.555%	$141.902	$141.90	$141.90	$141.90
Purchase #7	$243.61	13.195%	$275.7543	$275.75	$275.75	$275.80
7 purchase totals =	$898.24		$979.5317	$979.53	$979.55	$979.50