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	$211.53	10.174%	$233.0511	$233.05	$233.05	$233.10
Purchase #2	$44.83	13.717%	$50.9793	$50.98	$51.00	$51.00
Purchase #3	$78.59	13.398%	$89.1195	$89.12	$89.10	$89.10
Purchase #4	$219.72	9.272%	$240.0924	$240.09	$240.10	$240.10
Purchase #5	$109.76	12.357%	$123.323	$123.32	$123.30	$123.30
Purchase #6	$24.92	8.466%	$27.0297	$27.03	$27.05	$27.00
Purchase #7	$38.74	3.758%	$40.1958	$40.20	$40.20	$40.20
7 purchase totals =	$728.09		$803.7908	$803.79	$803.80	$803.80