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	$51.76	5.485%	$54.599	$54.60	$54.60	$54.60
Purchase #2	$46.86	7.304%	$50.2827	$50.28	$50.30	$50.30
Purchase #3	$187.82	10.541%	$207.6181	$207.62	$207.60	$207.60
Purchase #4	$66.53	7.234%	$71.3428	$71.34	$71.35	$71.30
Purchase #5	$183.97	13.119%	$208.105	$208.11	$208.10	$208.10
Purchase #6	$235.29	13.852%	$267.8824	$267.88	$267.90	$267.90
Purchase #7	$129.79	9.806%	$142.5172	$142.52	$142.50	$142.50
7 purchase totals =	$902.02		$1,002.3472	$1,002.35	$1,002.35	$1,002.30