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	$117.65	11.428%	$131.095	$131.10	$131.10	$131.10
Purchase #2	$32.56	10.473%	$35.97	$35.97	$35.95	$36.00
Purchase #3	$167.61	10.828%	$185.7588	$185.76	$185.75	$185.80
Purchase #4	$194.45	10.820%	$215.4895	$215.49	$215.50	$215.50
Purchase #5	$148.37	5.762%	$156.9191	$156.92	$156.90	$156.90
Purchase #6	$63.78	12.230%	$71.5803	$71.58	$71.60	$71.60
Purchase #7	$142.91	3.847%	$148.4077	$148.41	$148.40	$148.40
7 purchase totals =	$867.33		$945.2204	$945.23	$945.20	$945.30