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	$167.74	10.748%	$185.7687	$185.77	$185.75	$185.80
Purchase #2	$75.86	9.422%	$83.0075	$83.01	$83.00	$83.00
Purchase #3	$225.82	8.627%	$245.3015	$245.30	$245.30	$245.30
Purchase #4	$250.53	6.108%	$265.8324	$265.83	$265.85	$265.80
Purchase #5	$129.39	6.582%	$137.9064	$137.91	$137.90	$137.90
Purchase #6	$10.37	7.370%	$11.1343	$11.13	$11.15	$11.10
Purchase #7	$224.42	10.310%	$247.5577	$247.56	$247.55	$247.60
7 purchase totals =	$1,084.13		$1,176.5085	$1,176.51	$1,176.50	$1,176.50