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	$11.27	6.771%	$12.0331	$12.03	$12.05	$12.00
Purchase #2	$100.44	4.773%	$105.234	$105.23	$105.25	$105.20
Purchase #3	$220.85	9.737%	$242.3542	$242.35	$242.35	$242.40
Purchase #4	$189.30	3.552%	$196.0239	$196.02	$196.00	$196.00
Purchase #5	$184.79	13.711%	$210.1266	$210.13	$210.15	$210.10
Purchase #6	$240.28	5.676%	$253.9183	$253.92	$253.90	$253.90
Purchase #7	$242.88	10.716%	$268.907	$268.91	$268.90	$268.90
7 purchase totals =	$1,189.81		$1,288.5971	$1,288.59	$1,288.60	$1,288.50