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	$114.92	8.265%	$124.4181	$124.42	$124.40	$124.40
Purchase #2	$209.41	6.345%	$222.6971	$222.70	$222.70	$222.70
Purchase #3	$236.61	11.822%	$264.582	$264.58	$264.60	$264.60
Purchase #4	$113.42	13.164%	$128.3506	$128.35	$128.35	$128.40
Purchase #5	$222.42	9.744%	$244.0926	$244.09	$244.10	$244.10
Purchase #6	$17.30	9.355%	$18.9184	$18.92	$18.90	$18.90
Purchase #7	$131.96	7.444%	$141.7831	$141.78	$141.80	$141.80
7 purchase totals =	$1,046.04		$1,144.8419	$1,144.84	$1,144.85	$1,144.90