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	$131.44	11.765%	$146.9039	$146.90	$146.90	$146.90
Purchase #2	$31.48	7.711%	$33.9074	$33.91	$33.90	$33.90
Purchase #3	$113.33	9.639%	$124.2539	$124.25	$124.25	$124.30
Purchase #4	$234.61	13.660%	$266.6577	$266.66	$266.65	$266.70
Purchase #5	$28.76	8.356%	$31.1632	$31.16	$31.15	$31.20
Purchase #6	$171.79	8.223%	$185.9163	$185.92	$185.90	$185.90
Purchase #7	$218.77	7.247%	$234.6243	$234.62	$234.60	$234.60
7 purchase totals =	$930.18		$1,023.4267	$1,023.42	$1,023.35	$1,023.50