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	$163.70	6.537%	$174.4011	$174.40	$174.40	$174.40
Purchase #2	$173.34	4.375%	$180.9236	$180.92	$180.90	$180.90
Purchase #3	$67.58	13.689%	$76.831	$76.83	$76.85	$76.80
Purchase #4	$186.89	5.386%	$196.9559	$196.96	$196.95	$197.00
Purchase #5	$162.94	4.340%	$170.0116	$170.01	$170.00	$170.00
Purchase #6	$214.66	6.825%	$229.3105	$229.31	$229.30	$229.30
Purchase #7	$91.43	9.846%	$100.4322	$100.43	$100.45	$100.40
7 purchase totals =	$1,060.54		$1,128.8659	$1,128.86	$1,128.85	$1,128.80