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	$48.82	11.705%	$54.5344	$54.53	$54.55	$54.50
Purchase #2	$195.99	7.301%	$210.2992	$210.30	$210.30	$210.30
Purchase #3	$56.96	3.763%	$59.1034	$59.10	$59.10	$59.10
Purchase #4	$69.88	11.696%	$78.0532	$78.05	$78.05	$78.10
Purchase #5	$17.39	10.286%	$19.1787	$19.18	$19.20	$19.20
Purchase #6	$181.25	9.344%	$198.186	$198.19	$198.20	$198.20
Purchase #7	$118.43	11.168%	$131.6563	$131.66	$131.65	$131.70
7 purchase totals =	$688.72		$751.0112	$751.01	$751.05	$751.10