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	$42.73	12.568%	$48.1003	$48.10	$48.10	$48.10
Purchase #2	$126.88	11.220%	$141.1159	$141.12	$141.10	$141.10
Purchase #3	$98.92	4.713%	$103.5821	$103.58	$103.60	$103.60
Purchase #4	$97.38	3.431%	$100.7211	$100.72	$100.70	$100.70
Purchase #5	$6.93	5.705%	$7.3254	$7.33	$7.35	$7.30
Purchase #6	$159.48	12.760%	$179.8296	$179.83	$179.85	$179.80
Purchase #7	$181.74	8.702%	$197.555	$197.56	$197.55	$197.60
7 purchase totals =	$714.06		$778.2294	$778.24	$778.25	$778.20