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	$233.59	9.436%	$255.6316	$255.63	$255.65	$255.60
Purchase #2	$33.38	4.486%	$34.8774	$34.88	$34.90	$34.90
Purchase #3	$143.79	3.160%	$148.3338	$148.33	$148.35	$148.30
Purchase #4	$203.61	3.809%	$211.3655	$211.37	$211.35	$211.40
Purchase #5	$141.72	11.765%	$158.3934	$158.39	$158.40	$158.40
Purchase #6	$205.38	11.861%	$229.7401	$229.74	$229.75	$229.70
Purchase #7	$114.53	12.613%	$128.9757	$128.98	$129.00	$129.00
7 purchase totals =	$1,076.00		$1,167.3175	$1,167.32	$1,167.40	$1,167.30