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	$84.45	7.640%	$90.902	$90.90	$90.90	$90.90
Purchase #2	$100.75	4.788%	$105.5739	$105.57	$105.55	$105.60
Purchase #3	$177.80	12.833%	$200.6171	$200.62	$200.60	$200.60
Purchase #4	$180.49	3.110%	$186.1032	$186.10	$186.10	$186.10
Purchase #5	$219.69	11.476%	$244.9016	$244.90	$244.90	$244.90
Purchase #6	$181.55	13.638%	$206.3098	$206.31	$206.30	$206.30
Purchase #7	$67.89	13.216%	$76.8623	$76.86	$76.85	$76.90
7 purchase totals =	$1,012.62		$1,111.2699	$1,111.26	$1,111.20	$1,111.30