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	$199.56	9.308%	$218.135	$218.14	$218.15	$218.10
Purchase #2	$167.45	10.646%	$185.2767	$185.28	$185.30	$185.30
Purchase #3	$250.65	8.355%	$271.5918	$271.59	$271.60	$271.60
Purchase #4	$145.45	4.460%	$151.9371	$151.94	$151.95	$151.90
Purchase #5	$62.86	4.462%	$65.6648	$65.66	$65.65	$65.70
Purchase #6	$51.46	7.200%	$55.1651	$55.17	$55.15	$55.20
Purchase #7	$83.84	3.448%	$86.7308	$86.73	$86.75	$86.70
7 purchase totals =	$961.27		$1,034.5013	$1,034.51	$1,034.55	$1,034.50