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	$155.74	10.863%	$172.658	$172.66	$172.65	$172.70
Purchase #2	$75.73	3.543%	$78.4131	$78.41	$78.40	$78.40
Purchase #3	$80.34	6.206%	$85.3259	$85.33	$85.35	$85.30
Purchase #4	$243.65	8.405%	$264.1288	$264.13	$264.15	$264.10
Purchase #5	$109.28	12.595%	$123.0438	$123.04	$123.05	$123.00
Purchase #6	$13.56	12.630%	$15.2726	$15.27	$15.25	$15.30
Purchase #7	$250.58	6.511%	$266.8953	$266.90	$266.90	$266.90
7 purchase totals =	$928.88		$1,005.7375	$1,005.74	$1,005.75	$1,005.70