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	$137.37	13.860%	$156.4095	$156.41	$156.40	$156.40
Purchase #2	$96.59	8.206%	$104.5162	$104.52	$104.50	$104.50
Purchase #3	$45.40	7.630%	$48.864	$48.86	$48.85	$48.90
Purchase #4	$133.97	13.232%	$151.6969	$151.70	$151.70	$151.70
Purchase #5	$13.56	11.286%	$15.0904	$15.09	$15.10	$15.10
Purchase #6	$216.32	7.212%	$231.921	$231.92	$231.90	$231.90
Purchase #7	$223.61	4.488%	$233.6456	$233.65	$233.65	$233.60
7 purchase totals =	$866.82		$942.1436	$942.15	$942.10	$942.10