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	$64.98	5.565%	$68.5961	$68.60	$68.60	$68.60
Purchase #2	$140.64	9.370%	$153.818	$153.82	$153.80	$153.80
Purchase #3	$141.66	6.174%	$150.4061	$150.41	$150.40	$150.40
Purchase #4	$48.27	13.513%	$54.7927	$54.79	$54.80	$54.80
Purchase #5	$162.46	7.586%	$174.7842	$174.78	$174.80	$174.80
Purchase #6	$247.96	12.719%	$279.498	$279.50	$279.50	$279.50
Purchase #7	$160.64	9.476%	$175.8622	$175.86	$175.85	$175.90
7 purchase totals =	$966.61		$1,057.7573	$1,057.76	$1,057.75	$1,057.80