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	$90.35	10.535%	$99.8684	$99.87	$99.85	$99.90
Purchase #2	$231.99	9.706%	$254.5069	$254.51	$254.50	$254.50
Purchase #3	$195.88	11.384%	$218.179	$218.18	$218.20	$218.20
Purchase #4	$152.35	11.499%	$169.8687	$169.87	$169.85	$169.90
Purchase #5	$84.59	7.616%	$91.0324	$91.03	$91.05	$91.00
Purchase #6	$169.68	9.366%	$185.5722	$185.57	$185.55	$185.60
Purchase #7	$43.81	4.400%	$45.7376	$45.74	$45.75	$45.70
7 purchase totals =	$968.65		$1,064.7652	$1,064.77	$1,064.75	$1,064.80