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	$158.68	6.713%	$169.3322	$169.33	$169.35	$169.30
Purchase #2	$78.67	11.219%	$87.496	$87.50	$87.50	$87.50
Purchase #3	$231.32	9.435%	$253.145	$253.15	$253.15	$253.10
Purchase #4	$73.88	6.612%	$78.7649	$78.76	$78.75	$78.80
Purchase #5	$45.54	10.590%	$50.3627	$50.36	$50.35	$50.40
Purchase #6	$95.52	6.484%	$101.7135	$101.71	$101.70	$101.70
Purchase #7	$180.68	3.856%	$187.647	$187.65	$187.65	$187.60
7 purchase totals =	$864.29		$928.4613	$928.46	$928.45	$928.40