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	$88.43	6.717%	$94.3698	$94.37	$94.35	$94.40
Purchase #2	$59.43	11.860%	$66.4784	$66.48	$66.50	$66.50
Purchase #3	$123.48	5.556%	$130.3405	$130.34	$130.35	$130.30
Purchase #4	$84.56	6.670%	$90.2002	$90.20	$90.20	$90.20
Purchase #5	$90.70	9.446%	$99.2675	$99.27	$99.25	$99.30
Purchase #6	$176.42	11.442%	$196.606	$196.61	$196.60	$196.60
Purchase #7	$89.74	10.218%	$98.9096	$98.91	$98.90	$98.90
7 purchase totals =	$712.76		$776.1720	$776.18	$776.15	$776.20