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	$147.73	11.247%	$164.3452	$164.35	$164.35	$164.30
Purchase #2	$104.70	6.748%	$111.7652	$111.77	$111.75	$111.80
Purchase #3	$144.33	6.625%	$153.8919	$153.89	$153.90	$153.90
Purchase #4	$185.27	11.807%	$207.1448	$207.14	$207.15	$207.10
Purchase #5	$71.95	9.471%	$78.7644	$78.76	$78.75	$78.80
Purchase #6	$93.36	10.259%	$102.9378	$102.94	$102.95	$102.90
Purchase #7	$27.60	10.316%	$30.4472	$30.45	$30.45	$30.40
7 purchase totals =	$774.94		$849.2965	$849.30	$849.30	$849.20