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	$197.62	4.575%	$206.6611	$206.66	$206.65	$206.70
Purchase #2	$55.65	7.524%	$59.8371	$59.84	$59.85	$59.80
Purchase #3	$52.39	4.474%	$54.7339	$54.73	$54.75	$54.70
Purchase #4	$42.67	11.572%	$47.6078	$47.61	$47.60	$47.60
Purchase #5	$25.44	12.347%	$28.5811	$28.58	$28.60	$28.60
Purchase #6	$233.33	13.305%	$264.3746	$264.37	$264.35	$264.40
Purchase #7	$72.31	10.758%	$80.0891	$80.09	$80.10	$80.10
7 purchase totals =	$679.41		$741.8847	$741.88	$741.90	$741.90