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	$70.84	3.607%	$73.3952	$73.40	$73.40	$73.40
Purchase #2	$236.80	5.802%	$250.5391	$250.54	$250.55	$250.50
Purchase #3	$14.72	3.457%	$15.2289	$15.23	$15.25	$15.20
Purchase #4	$42.96	5.231%	$45.2072	$45.21	$45.20	$45.20
Purchase #5	$127.41	7.345%	$136.7683	$136.77	$136.75	$136.80
Purchase #6	$109.80	3.834%	$114.0097	$114.01	$114.00	$114.00
Purchase #7	$55.35	7.119%	$59.2904	$59.29	$59.30	$59.30
7 purchase totals =	$657.88		$694.4388	$694.45	$694.45	$694.40