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	$122.94	3.665%	$127.4458	$127.45	$127.45	$127.40
Purchase #2	$160.26	4.842%	$168.0198	$168.02	$168.00	$168.00
Purchase #3	$187.76	12.124%	$210.524	$210.52	$210.50	$210.50
Purchase #4	$185.77	7.711%	$200.0947	$200.09	$200.10	$200.10
Purchase #5	$48.69	6.495%	$51.8524	$51.85	$51.85	$51.90
Purchase #6	$53.36	4.446%	$55.7324	$55.73	$55.75	$55.70
Purchase #7	$42.41	12.399%	$47.6684	$47.67	$47.65	$47.70
7 purchase totals =	$801.19		$861.3375	$861.33	$861.30	$861.30