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	$90.36	5.629%	$95.4464	$95.45	$95.45	$95.40
Purchase #2	$143.88	5.829%	$152.2668	$152.27	$152.25	$152.30
Purchase #3	$30.51	12.150%	$34.217	$34.22	$34.20	$34.20
Purchase #4	$221.40	6.754%	$236.3534	$236.35	$236.35	$236.40
Purchase #5	$162.92	9.262%	$178.0097	$178.01	$178.00	$178.00
Purchase #6	$77.50	3.872%	$80.5008	$80.50	$80.50	$80.50
Purchase #7	$54.45	9.694%	$59.7284	$59.73	$59.75	$59.70
7 purchase totals =	$781.02		$836.5225	$836.53	$836.50	$836.50