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	$100.43	9.408%	$109.8785	$109.88	$109.90	$109.90
Purchase #2	$236.78	11.231%	$263.3728	$263.37	$263.35	$263.40
Purchase #3	$41.61	13.874%	$47.383	$47.38	$47.40	$47.40
Purchase #4	$200.77	7.865%	$216.5606	$216.56	$216.55	$216.60
Purchase #5	$143.53	3.216%	$148.1459	$148.15	$148.15	$148.10
Purchase #6	$35.67	7.187%	$38.2336	$38.23	$38.25	$38.20
Purchase #7	$237.42	5.484%	$250.4401	$250.44	$250.45	$250.40
7 purchase totals =	$996.21		$1,074.0145	$1,074.01	$1,074.05	$1,074.00