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	$117.88	4.862%	$123.6113	$123.61	$123.60	$123.60
Purchase #2	$18.42	10.212%	$20.3011	$20.30	$20.30	$20.30
Purchase #3	$84.99	10.842%	$94.2046	$94.20	$94.20	$94.20
Purchase #4	$55.75	12.174%	$62.537	$62.54	$62.55	$62.50
Purchase #5	$41.76	4.271%	$43.5436	$43.54	$43.55	$43.50
Purchase #6	$73.94	6.518%	$78.7594	$78.76	$78.75	$78.80
Purchase #7	$141.96	6.490%	$151.1732	$151.17	$151.15	$151.20
7 purchase totals =	$534.70		$574.1302	$574.12	$574.10	$574.10