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	$96.53	5.367%	$101.7108	$101.71	$101.70	$101.70
Purchase #2	$54.45	4.489%	$56.8943	$56.89	$56.90	$56.90
Purchase #3	$120.77	8.294%	$130.7867	$130.79	$130.80	$130.80
Purchase #4	$198.80	10.528%	$219.7297	$219.73	$219.75	$219.70
Purchase #5	$230.77	6.352%	$245.4285	$245.43	$245.45	$245.40
Purchase #6	$128.88	6.308%	$137.0098	$137.01	$137.00	$137.00
Purchase #7	$118.97	7.631%	$128.0486	$128.05	$128.05	$128.00
7 purchase totals =	$949.17		$1,019.6084	$1,019.61	$1,019.65	$1,019.50