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	$182.90	7.516%	$196.6468	$196.65	$196.65	$196.60
Purchase #2	$67.62	3.466%	$69.9637	$69.96	$69.95	$70.00
Purchase #3	$197.58	12.705%	$222.6825	$222.68	$222.70	$222.70
Purchase #4	$123.84	6.293%	$131.6333	$131.63	$131.65	$131.60
Purchase #5	$245.91	7.636%	$264.6877	$264.69	$264.70	$264.70
Purchase #6	$80.99	13.457%	$91.8888	$91.89	$91.90	$91.90
Purchase #7	$125.28	6.669%	$133.6349	$133.63	$133.65	$133.60
7 purchase totals =	$1,024.12		$1,111.1377	$1,111.13	$1,111.20	$1,111.10