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	$180.46	7.662%	$194.2868	$194.29	$194.30	$194.30
Purchase #2	$152.89	7.686%	$164.6411	$164.64	$164.65	$164.60
Purchase #3	$250.93	8.161%	$271.4084	$271.41	$271.40	$271.40
Purchase #4	$91.90	7.526%	$98.8164	$98.82	$98.80	$98.80
Purchase #5	$57.36	4.431%	$59.9016	$59.90	$59.90	$59.90
Purchase #6	$247.26	11.342%	$275.3042	$275.30	$275.30	$275.30
Purchase #7	$88.96	6.494%	$94.7371	$94.74	$94.75	$94.70
7 purchase totals =	$1,069.76		$1,159.0956	$1,159.10	$1,159.10	$1,159.00