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	$146.74	6.475%	$156.2414	$156.24	$156.25	$156.20
Purchase #2	$84.89	13.809%	$96.6125	$96.61	$96.60	$96.60
Purchase #3	$235.67	11.215%	$262.1004	$262.10	$262.10	$262.10
Purchase #4	$167.74	10.448%	$185.2655	$185.27	$185.25	$185.30
Purchase #5	$164.64	6.834%	$175.8915	$175.89	$175.90	$175.90
Purchase #6	$18.88	7.127%	$20.2256	$20.23	$20.25	$20.20
Purchase #7	$197.52	9.740%	$216.7584	$216.76	$216.75	$216.80
7 purchase totals =	$1,016.08		$1,113.0953	$1,113.10	$1,113.10	$1,113.10