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	$158.35	4.234%	$165.0545	$165.05	$165.05	$165.10
Purchase #2	$141.41	13.219%	$160.103	$160.10	$160.10	$160.10
Purchase #3	$136.77	3.410%	$141.4339	$141.43	$141.45	$141.40
Purchase #4	$25.57	13.237%	$28.9547	$28.95	$28.95	$29.00
Purchase #5	$85.72	11.409%	$95.4998	$95.50	$95.50	$95.50
Purchase #6	$91.86	8.523%	$99.6892	$99.69	$99.70	$99.70
Purchase #7	$168.83	10.271%	$186.1705	$186.17	$186.15	$186.20
7 purchase totals =	$808.51		$876.9056	$876.89	$876.90	$877.00