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	$129.70	10.705%	$143.5844	$143.58	$143.60	$143.60
Purchase #2	$90.55	8.681%	$98.4106	$98.41	$98.40	$98.40
Purchase #3	$96.59	3.781%	$100.2421	$100.24	$100.25	$100.20
Purchase #4	$137.65	13.777%	$156.614	$156.61	$156.60	$156.60
Purchase #5	$189.77	9.377%	$207.5647	$207.56	$207.55	$207.60
Purchase #6	$103.64	10.172%	$114.1823	$114.18	$114.20	$114.20
Purchase #7	$188.42	11.796%	$210.646	$210.65	$210.65	$210.60
7 purchase totals =	$936.32		$1,031.2441	$1,031.23	$1,031.25	$1,031.20