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	$141.33	3.581%	$146.391	$146.39	$146.40	$146.40
Purchase #2	$240.32	7.307%	$257.8802	$257.88	$257.90	$257.90
Purchase #3	$8.83	13.873%	$10.055	$10.06	$10.05	$10.10
Purchase #4	$119.61	8.600%	$129.8965	$129.90	$129.90	$129.90
Purchase #5	$154.69	7.252%	$165.9081	$165.91	$165.90	$165.90
Purchase #6	$227.36	6.571%	$242.2998	$242.30	$242.30	$242.30
Purchase #7	$102.57	8.542%	$111.3315	$111.33	$111.35	$111.30
7 purchase totals =	$994.71		$1,063.7621	$1,063.77	$1,063.80	$1,063.80