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	$144.54	6.557%	$154.0175	$154.02	$154.00	$154.00
Purchase #2	$170.70	8.221%	$184.7332	$184.73	$184.75	$184.70
Purchase #3	$107.39	3.469%	$111.1154	$111.12	$111.10	$111.10
Purchase #4	$234.89	11.474%	$261.8413	$261.84	$261.85	$261.80
Purchase #5	$92.74	7.330%	$99.5378	$99.54	$99.55	$99.50
Purchase #6	$198.48	6.756%	$211.8893	$211.89	$211.90	$211.90
Purchase #7	$115.73	12.116%	$129.7518	$129.75	$129.75	$129.80
7 purchase totals =	$1,064.47		$1,152.8863	$1,152.89	$1,152.90	$1,152.80