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	$32.38	8.337%	$35.0795	$35.08	$35.10	$35.10
Purchase #2	$187.49	8.301%	$203.0535	$203.05	$203.05	$203.10
Purchase #3	$250.38	4.336%	$261.2365	$261.24	$261.25	$261.20
Purchase #4	$184.30	6.549%	$196.3698	$196.37	$196.35	$196.40
Purchase #5	$96.35	4.494%	$100.68	$100.68	$100.70	$100.70
Purchase #6	$107.39	4.344%	$112.055	$112.06	$112.05	$112.10
Purchase #7	$97.72	7.124%	$104.6816	$104.68	$104.70	$104.70
7 purchase totals =	$956.01		$1,013.1559	$1,013.16	$1,013.20	$1,013.30