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	$235.71	11.234%	$262.1897	$262.19	$262.20	$262.20
Purchase #2	$82.52	3.851%	$85.6978	$85.70	$85.70	$85.70
Purchase #3	$233.70	12.665%	$263.2981	$263.30	$263.30	$263.30
Purchase #4	$101.99	10.779%	$112.9835	$112.98	$113.00	$113.00
Purchase #5	$142.74	13.538%	$162.0641	$162.06	$162.05	$162.10
Purchase #6	$85.50	10.797%	$94.7314	$94.73	$94.75	$94.70
Purchase #7	$35.96	3.798%	$37.3258	$37.33	$37.35	$37.30
7 purchase totals =	$918.12		$1,018.2904	$1,018.29	$1,018.35	$1,018.30