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	$115.61	10.547%	$127.8034	$127.80	$127.80	$127.80
Purchase #2	$51.78	4.106%	$53.9061	$53.91	$53.90	$53.90
Purchase #3	$28.85	3.618%	$29.8938	$29.89	$29.90	$29.90
Purchase #4	$151.27	8.679%	$164.3987	$164.40	$164.40	$164.40
Purchase #5	$180.80	4.435%	$188.8185	$188.82	$188.80	$188.80
Purchase #6	$47.81	3.295%	$49.3853	$49.39	$49.40	$49.40
Purchase #7	$205.60	13.302%	$232.9489	$232.95	$232.95	$232.90
7 purchase totals =	$781.72		$847.1547	$847.16	$847.15	$847.10