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	$181.34	10.787%	$200.9011	$200.90	$200.90	$200.90
Purchase #2	$145.98	4.478%	$152.517	$152.52	$152.50	$152.50
Purchase #3	$80.53	13.174%	$91.139	$91.14	$91.15	$91.10
Purchase #4	$47.36	7.176%	$50.7586	$50.76	$50.75	$50.80
Purchase #5	$168.49	7.803%	$181.6373	$181.64	$181.65	$181.60
Purchase #6	$168.72	4.254%	$175.8973	$175.90	$175.90	$175.90
Purchase #7	$59.54	7.507%	$64.0097	$64.01	$64.00	$64.00
7 purchase totals =	$851.96		$916.8600	$916.87	$916.85	$916.80