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	$242.95	10.108%	$267.5074	$267.51	$267.50	$267.50
Purchase #2	$115.96	9.341%	$126.7918	$126.79	$126.80	$126.80
Purchase #3	$169.73	7.169%	$181.8979	$181.90	$181.90	$181.90
Purchase #4	$181.91	8.195%	$196.8175	$196.82	$196.80	$196.80
Purchase #5	$32.30	11.132%	$35.8956	$35.90	$35.90	$35.90
Purchase #6	$36.59	13.416%	$41.4989	$41.50	$41.50	$41.50
Purchase #7	$152.48	5.809%	$161.3376	$161.34	$161.35	$161.30
7 purchase totals =	$931.92		$1,011.7467	$1,011.76	$1,011.75	$1,011.70