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	$32.90	7.156%	$35.2543	$35.25	$35.25	$35.30
Purchase #2	$100.51	7.185%	$107.7316	$107.73	$107.75	$107.70
Purchase #3	$167.91	8.484%	$182.1555	$182.16	$182.15	$182.20
Purchase #4	$140.89	10.568%	$155.7793	$155.78	$155.80	$155.80
Purchase #5	$112.76	13.275%	$127.7289	$127.73	$127.75	$127.70
Purchase #6	$212.38	11.408%	$236.6083	$236.61	$236.60	$236.60
Purchase #7	$141.66	10.787%	$156.9409	$156.94	$156.95	$156.90
7 purchase totals =	$909.01		$1,002.1988	$1,002.20	$1,002.25	$1,002.20