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	$90.99	9.722%	$99.836	$99.84	$99.85	$99.80
Purchase #2	$45.31	5.191%	$47.662	$47.66	$47.65	$47.70
Purchase #3	$110.97	11.150%	$123.3432	$123.34	$123.35	$123.30
Purchase #4	$188.65	10.326%	$208.13	$208.13	$208.15	$208.10
Purchase #5	$241.72	10.705%	$267.5961	$267.60	$267.60	$267.60
Purchase #6	$207.31	7.686%	$223.2438	$223.24	$223.25	$223.20
Purchase #7	$166.94	11.212%	$185.6573	$185.66	$185.65	$185.70
7 purchase totals =	$1,051.89		$1,155.4684	$1,155.47	$1,155.50	$1,155.40