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	$55.47	7.556%	$59.6613	$59.66	$59.65	$59.70
Purchase #2	$54.64	12.514%	$61.4776	$61.48	$61.50	$61.50
Purchase #3	$67.69	6.494%	$72.0858	$72.09	$72.10	$72.10
Purchase #4	$52.92	8.869%	$57.6135	$57.61	$57.60	$57.60
Purchase #5	$72.77	3.768%	$75.512	$75.51	$75.50	$75.50
Purchase #6	$45.36	7.750%	$48.8754	$48.88	$48.90	$48.90
Purchase #7	$156.44	12.475%	$175.9559	$175.96	$175.95	$176.00
7 purchase totals =	$505.29		$551.1815	$551.19	$551.20	$551.30