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	$23.98	3.698%	$24.8668	$24.87	$24.85	$24.90
Purchase #2	$118.32	7.418%	$127.097	$127.10	$127.10	$127.10
Purchase #3	$94.95	10.738%	$105.1457	$105.15	$105.15	$105.10
Purchase #4	$28.91	7.796%	$31.1638	$31.16	$31.15	$31.20
Purchase #5	$56.50	8.137%	$61.0974	$61.10	$61.10	$61.10
Purchase #6	$223.64	4.681%	$234.1086	$234.11	$234.10	$234.10
Purchase #7	$109.88	10.156%	$121.0394	$121.04	$121.05	$121.00
7 purchase totals =	$656.18		$704.5187	$704.53	$704.50	$704.50