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	$90.69	12.612%	$102.1278	$102.13	$102.15	$102.10
Purchase #2	$241.33	11.841%	$269.9059	$269.91	$269.90	$269.90
Purchase #3	$14.56	7.184%	$15.606	$15.61	$15.60	$15.60
Purchase #4	$59.73	3.276%	$61.6868	$61.69	$61.70	$61.70
Purchase #5	$136.88	6.172%	$145.3282	$145.33	$145.35	$145.30
Purchase #6	$166.36	7.810%	$179.3527	$179.35	$179.35	$179.40
Purchase #7	$236.62	5.129%	$248.7562	$248.76	$248.75	$248.80
7 purchase totals =	$946.17		$1,022.7636	$1,022.78	$1,022.80	$1,022.80