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	$167.40	10.866%	$185.5897	$185.59	$185.60	$185.60
Purchase #2	$207.98	6.760%	$222.0394	$222.04	$222.05	$222.00
Purchase #3	$119.53	9.328%	$130.6798	$130.68	$130.70	$130.70
Purchase #4	$185.27	10.366%	$204.4751	$204.48	$204.50	$204.50
Purchase #5	$141.72	9.382%	$155.0162	$155.02	$155.00	$155.00
Purchase #6	$209.49	6.385%	$222.8659	$222.87	$222.85	$222.90
Purchase #7	$161.49	10.498%	$178.4432	$178.44	$178.45	$178.40
7 purchase totals =	$1,192.88		$1,299.1093	$1,299.12	$1,299.15	$1,299.10