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	$244.30	12.425%	$274.6543	$274.65	$274.65	$274.70
Purchase #2	$79.36	4.461%	$82.9002	$82.90	$82.90	$82.90
Purchase #3	$83.52	4.131%	$86.9702	$86.97	$86.95	$87.00
Purchase #4	$150.92	6.801%	$161.1841	$161.18	$161.20	$161.20
Purchase #5	$148.26	9.338%	$162.1045	$162.10	$162.10	$162.10
Purchase #6	$57.72	3.330%	$59.6421	$59.64	$59.65	$59.60
Purchase #7	$236.61	3.560%	$245.0333	$245.03	$245.05	$245.00
7 purchase totals =	$1,000.69		$1,072.4887	$1,072.47	$1,072.50	$1,072.50