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	$236.95	9.796%	$260.1616	$260.16	$260.15	$260.20
Purchase #2	$54.42	10.449%	$60.1063	$60.11	$60.10	$60.10
Purchase #3	$123.44	10.627%	$136.558	$136.56	$136.55	$136.60
Purchase #4	$176.35	6.652%	$188.0808	$188.08	$188.10	$188.10
Purchase #5	$204.28	7.479%	$219.5581	$219.56	$219.55	$219.60
Purchase #6	$54.83	8.449%	$59.4626	$59.46	$59.45	$59.50
Purchase #7	$231.28	6.196%	$245.6101	$245.61	$245.60	$245.60
7 purchase totals =	$1,081.55		$1,169.5375	$1,169.54	$1,169.50	$1,169.70