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	$200.55	5.161%	$210.9004	$210.90	$210.90	$210.90
Purchase #2	$204.87	13.826%	$233.1953	$233.20	$233.20	$233.20
Purchase #3	$234.93	4.848%	$246.3194	$246.32	$246.30	$246.30
Purchase #4	$92.89	6.822%	$99.227	$99.23	$99.25	$99.20
Purchase #5	$30.70	9.366%	$33.5754	$33.58	$33.60	$33.60
Purchase #6	$146.89	10.788%	$162.7365	$162.74	$162.75	$162.70
Purchase #7	$168.69	9.336%	$184.4389	$184.44	$184.45	$184.40
7 purchase totals =	$1,079.52		$1,170.3929	$1,170.41	$1,170.45	$1,170.30