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	$245.63	10.551%	$271.5464	$271.55	$271.55	$271.50
Purchase #2	$234.25	6.275%	$248.9492	$248.95	$248.95	$248.90
Purchase #3	$17.79	4.354%	$18.5646	$18.56	$18.55	$18.60
Purchase #4	$57.51	3.451%	$59.4947	$59.49	$59.50	$59.50
Purchase #5	$89.47	8.137%	$96.7502	$96.75	$96.75	$96.80
Purchase #6	$62.77	5.243%	$66.061	$66.06	$66.05	$66.10
Purchase #7	$241.67	3.774%	$250.7906	$250.79	$250.80	$250.80
7 purchase totals =	$949.09		$1,012.1567	$1,012.15	$1,012.15	$1,012.20