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	$60.75	3.280%	$62.7426	$62.74	$62.75	$62.70
Purchase #2	$247.49	8.124%	$267.5961	$267.60	$267.60	$267.60
Purchase #3	$173.69	5.128%	$182.5968	$182.60	$182.60	$182.60
Purchase #4	$240.44	6.366%	$255.7464	$255.75	$255.75	$255.70
Purchase #5	$83.57	6.535%	$89.0313	$89.03	$89.05	$89.00
Purchase #6	$99.45	10.297%	$109.6904	$109.69	$109.70	$109.70
Purchase #7	$94.78	12.771%	$106.8844	$106.88	$106.90	$106.90
7 purchase totals =	$1,000.17		$1,074.2880	$1,074.29	$1,074.35	$1,074.20