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	$219.59	5.209%	$231.0284	$231.03	$231.05	$231.00
Purchase #2	$63.63	11.174%	$70.74	$70.74	$70.75	$70.70
Purchase #3	$78.29	5.655%	$82.7173	$82.72	$82.70	$82.70
Purchase #4	$40.69	11.371%	$45.3169	$45.32	$45.30	$45.30
Purchase #5	$194.46	11.269%	$216.3737	$216.37	$216.35	$216.40
Purchase #6	$220.48	6.182%	$234.1101	$234.11	$234.10	$234.10
Purchase #7	$29.77	4.609%	$31.1421	$31.14	$31.15	$31.10
7 purchase totals =	$846.91		$911.4285	$911.43	$911.40	$911.30