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	$108.74	13.415%	$123.3275	$123.33	$123.35	$123.30
Purchase #2	$157.31	6.645%	$167.7632	$167.76	$167.75	$167.80
Purchase #3	$23.83	5.734%	$25.1964	$25.20	$25.20	$25.20
Purchase #4	$175.53	13.659%	$199.5056	$199.51	$199.50	$199.50
Purchase #5	$51.72	8.465%	$56.0981	$56.10	$56.10	$56.10
Purchase #6	$231.82	9.355%	$253.5068	$253.51	$253.50	$253.50
Purchase #7	$236.50	13.804%	$269.1465	$269.15	$269.15	$269.10
7 purchase totals =	$985.45		$1,094.5441	$1,094.56	$1,094.55	$1,094.50