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	$147.54	3.336%	$152.4619	$152.46	$152.45	$152.50
Purchase #2	$190.61	6.779%	$203.5315	$203.53	$203.55	$203.50
Purchase #3	$217.59	6.243%	$231.1741	$231.17	$231.15	$231.20
Purchase #4	$49.31	13.318%	$55.8771	$55.88	$55.90	$55.90
Purchase #5	$212.61	13.305%	$240.8978	$240.90	$240.90	$240.90
Purchase #6	$246.29	10.138%	$271.2589	$271.26	$271.25	$271.30
Purchase #7	$175.74	5.360%	$185.1597	$185.16	$185.15	$185.20
7 purchase totals =	$1,239.69		$1,340.3610	$1,340.36	$1,340.35	$1,340.50