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	$113.44	12.192%	$127.2706	$127.27	$127.25	$127.30
Purchase #2	$202.31	11.721%	$226.0228	$226.02	$226.00	$226.00
Purchase #3	$198.82	5.807%	$210.3655	$210.37	$210.35	$210.40
Purchase #4	$49.46	9.765%	$54.2898	$54.29	$54.30	$54.30
Purchase #5	$101.96	9.625%	$111.7737	$111.77	$111.75	$111.80
Purchase #6	$67.96	12.113%	$76.192	$76.19	$76.20	$76.20
Purchase #7	$209.37	10.747%	$231.871	$231.87	$231.85	$231.90
7 purchase totals =	$943.32		$1,037.7854	$1,037.78	$1,037.70	$1,037.90