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	$184.53	8.459%	$200.1394	$200.14	$200.15	$200.10
Purchase #2	$229.56	3.793%	$238.2672	$238.27	$238.25	$238.30
Purchase #3	$199.69	12.104%	$223.8605	$223.86	$223.85	$223.90
Purchase #4	$241.83	9.272%	$264.2525	$264.25	$264.25	$264.30
Purchase #5	$32.61	5.274%	$34.3299	$34.33	$34.35	$34.30
Purchase #6	$47.68	8.260%	$51.6184	$51.62	$51.60	$51.60
Purchase #7	$232.60	6.802%	$248.4215	$248.42	$248.40	$248.40
7 purchase totals =	$1,168.50		$1,260.8894	$1,260.89	$1,260.85	$1,260.90