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	$134.43	8.524%	$145.8888	$145.89	$145.90	$145.90
Purchase #2	$82.61	8.717%	$89.8111	$89.81	$89.80	$89.80
Purchase #3	$168.52	9.782%	$185.0046	$185.00	$185.00	$185.00
Purchase #4	$231.69	8.669%	$251.7752	$251.78	$251.80	$251.80
Purchase #5	$168.62	7.594%	$181.425	$181.43	$181.45	$181.40
Purchase #6	$118.53	12.498%	$133.3439	$133.34	$133.35	$133.30
Purchase #7	$137.76	7.139%	$147.5947	$147.59	$147.60	$147.60
7 purchase totals =	$1,042.16		$1,134.8433	$1,134.84	$1,134.90	$1,134.80