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	$120.90	3.164%	$124.7253	$124.73	$124.75	$124.70
Purchase #2	$7.26	6.841%	$7.7567	$7.76	$7.75	$7.80
Purchase #3	$241.61	4.793%	$253.1904	$253.19	$253.20	$253.20
Purchase #4	$170.27	8.858%	$185.3525	$185.35	$185.35	$185.40
Purchase #5	$234.50	3.534%	$242.7872	$242.79	$242.80	$242.80
Purchase #6	$111.33	10.655%	$123.1922	$123.19	$123.20	$123.20
Purchase #7	$138.45	3.315%	$143.0396	$143.04	$143.05	$143.00
7 purchase totals =	$1,024.32		$1,080.0439	$1,080.05	$1,080.10	$1,080.10