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	$34.65	8.440%	$37.5745	$37.57	$37.55	$37.60
Purchase #2	$167.92	4.314%	$175.1641	$175.16	$175.15	$175.20
Purchase #3	$181.81	7.155%	$194.8185	$194.82	$194.80	$194.80
Purchase #4	$18.90	6.247%	$20.0807	$20.08	$20.10	$20.10
Purchase #5	$150.56	12.815%	$169.8543	$169.85	$169.85	$169.90
Purchase #6	$217.95	12.643%	$245.5054	$245.51	$245.50	$245.50
Purchase #7	$218.33	3.345%	$225.6331	$225.63	$225.65	$225.60
7 purchase totals =	$990.12		$1,068.6306	$1,068.62	$1,068.60	$1,068.70