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	$9.51	6.277%	$10.1069	$10.11	$10.10	$10.10
Purchase #2	$191.55	4.478%	$200.1276	$200.13	$200.15	$200.10
Purchase #3	$188.87	4.865%	$198.0585	$198.06	$198.05	$198.10
Purchase #4	$179.73	10.584%	$198.7526	$198.75	$198.75	$198.80
Purchase #5	$141.39	6.103%	$150.019	$150.02	$150.00	$150.00
Purchase #6	$217.77	9.501%	$238.4603	$238.46	$238.45	$238.50
Purchase #7	$37.75	13.616%	$42.89	$42.89	$42.90	$42.90
7 purchase totals =	$966.57		$1,038.4149	$1,038.42	$1,038.40	$1,038.50