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	$28.94	13.227%	$32.7679	$32.77	$32.75	$32.80
Purchase #2	$137.61	3.754%	$142.7759	$142.78	$142.80	$142.80
Purchase #3	$72.39	3.325%	$74.797	$74.80	$74.80	$74.80
Purchase #4	$224.46	11.721%	$250.769	$250.77	$250.75	$250.80
Purchase #5	$237.60	3.298%	$245.436	$245.44	$245.45	$245.40
Purchase #6	$156.42	12.424%	$175.8536	$175.85	$175.85	$175.90
Purchase #7	$112.89	13.840%	$128.514	$128.51	$128.50	$128.50
7 purchase totals =	$970.31		$1,050.9134	$1,050.92	$1,050.90	$1,051.00