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	$67.58	3.853%	$70.1839	$70.18	$70.20	$70.20
Purchase #2	$70.74	9.340%	$77.3471	$77.35	$77.35	$77.30
Purchase #3	$210.28	5.342%	$221.5132	$221.51	$221.50	$221.50
Purchase #4	$136.78	6.359%	$145.4778	$145.48	$145.50	$145.50
Purchase #5	$246.83	10.830%	$273.5617	$273.56	$273.55	$273.60
Purchase #6	$143.76	11.673%	$160.5411	$160.54	$160.55	$160.50
Purchase #7	$172.82	5.786%	$182.8194	$182.82	$182.80	$182.80
7 purchase totals =	$1,048.79		$1,131.4442	$1,131.44	$1,131.45	$1,131.40