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	$78.58	4.531%	$82.1405	$82.14	$82.15	$82.10
Purchase #2	$90.93	11.731%	$101.597	$101.60	$101.60	$101.60
Purchase #3	$18.73	9.187%	$20.4507	$20.45	$20.45	$20.50
Purchase #4	$159.69	13.548%	$181.3248	$181.32	$181.30	$181.30
Purchase #5	$129.86	13.468%	$147.3495	$147.35	$147.35	$147.30
Purchase #6	$51.54	4.615%	$53.9186	$53.92	$53.90	$53.90
Purchase #7	$99.69	8.340%	$108.0041	$108.00	$108.00	$108.00
7 purchase totals =	$629.02		$694.7852	$694.78	$694.75	$694.70