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	$43.27	9.304%	$47.2958	$47.30	$47.30	$47.30
Purchase #2	$59.55	4.628%	$62.306	$62.31	$62.30	$62.30
Purchase #3	$250.36	10.609%	$276.9207	$276.92	$276.90	$276.90
Purchase #4	$205.87	8.585%	$223.5439	$223.54	$223.55	$223.50
Purchase #5	$95.96	11.809%	$107.2919	$107.29	$107.30	$107.30
Purchase #6	$156.69	11.685%	$174.9992	$175.00	$175.00	$175.00
Purchase #7	$82.84	3.612%	$85.8322	$85.83	$85.85	$85.80
7 purchase totals =	$894.54		$978.1897	$978.19	$978.20	$978.10