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	$163.89	10.731%	$181.477	$181.48	$181.50	$181.50
Purchase #2	$196.27	12.507%	$220.8175	$220.82	$220.80	$220.80
Purchase #3	$163.94	11.115%	$182.1619	$182.16	$182.15	$182.20
Purchase #4	$56.54	10.167%	$62.2884	$62.29	$62.30	$62.30
Purchase #5	$175.78	13.304%	$199.1658	$199.17	$199.15	$199.20
Purchase #6	$57.88	11.519%	$64.5472	$64.55	$64.55	$64.50
Purchase #7	$96.39	10.744%	$106.7461	$106.75	$106.75	$106.70
7 purchase totals =	$910.69		$1,017.2039	$1,017.22	$1,017.20	$1,017.20