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	$206.46	13.268%	$233.8531	$233.85	$233.85	$233.90
Purchase #2	$152.74	6.636%	$162.8758	$162.88	$162.90	$162.90
Purchase #3	$34.52	5.560%	$36.4393	$36.44	$36.45	$36.40
Purchase #4	$103.84	5.796%	$109.8586	$109.86	$109.85	$109.90
Purchase #5	$62.88	10.622%	$69.5591	$69.56	$69.55	$69.60
Purchase #6	$122.56	11.185%	$136.2683	$136.27	$136.25	$136.30
Purchase #7	$46.59	9.290%	$50.9182	$50.92	$50.90	$50.90
7 purchase totals =	$729.59		$799.7724	$799.78	$799.75	$799.90