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	$84.48	9.277%	$92.3172	$92.32	$92.30	$92.30
Purchase #2	$243.33	11.842%	$272.1451	$272.15	$272.15	$272.10
Purchase #3	$73.28	6.843%	$78.2946	$78.29	$78.30	$78.30
Purchase #4	$42.70	3.704%	$44.2816	$44.28	$44.30	$44.30
Purchase #5	$41.94	9.416%	$45.8891	$45.89	$45.90	$45.90
Purchase #6	$228.91	4.865%	$240.0465	$240.05	$240.05	$240.00
Purchase #7	$249.50	5.414%	$263.0079	$263.01	$263.00	$263.00
7 purchase totals =	$964.14		$1,035.9820	$1,035.99	$1,036.00	$1,035.90