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	$188.42	13.351%	$213.576	$213.58	$213.60	$213.60
Purchase #2	$147.61	11.276%	$164.2545	$164.25	$164.25	$164.30
Purchase #3	$95.72	3.685%	$99.2473	$99.25	$99.25	$99.20
Purchase #4	$234.73	6.455%	$249.8818	$249.88	$249.90	$249.90
Purchase #5	$205.65	3.488%	$212.8231	$212.82	$212.80	$212.80
Purchase #6	$211.41	12.811%	$238.4937	$238.49	$238.50	$238.50
Purchase #7	$96.53	7.543%	$103.8113	$103.81	$103.80	$103.80
7 purchase totals =	$1,180.07		$1,282.0877	$1,282.08	$1,282.10	$1,282.10