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	$68.31	4.551%	$71.4188	$71.42	$71.40	$71.40
Purchase #2	$241.42	10.445%	$266.6363	$266.64	$266.65	$266.60
Purchase #3	$30.73	5.715%	$32.4862	$32.49	$32.50	$32.50
Purchase #4	$122.94	8.557%	$133.46	$133.46	$133.45	$133.50
Purchase #5	$233.91	13.258%	$264.9218	$264.92	$264.90	$264.90
Purchase #6	$133.98	5.535%	$141.3958	$141.40	$141.40	$141.40
Purchase #7	$137.47	8.499%	$149.1536	$149.15	$149.15	$149.20
7 purchase totals =	$968.76		$1,059.4725	$1,059.48	$1,059.45	$1,059.50