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	$77.27	9.229%	$84.4012	$84.40	$84.40	$84.40
Purchase #2	$213.96	10.168%	$235.7155	$235.72	$235.70	$235.70
Purchase #3	$165.76	5.323%	$174.5834	$174.58	$174.60	$174.60
Purchase #4	$90.89	7.759%	$97.9422	$97.94	$97.95	$97.90
Purchase #5	$187.47	12.179%	$210.302	$210.30	$210.30	$210.30
Purchase #6	$99.27	6.417%	$105.6402	$105.64	$105.65	$105.60
Purchase #7	$101.69	7.210%	$109.0218	$109.02	$109.00	$109.00
7 purchase totals =	$936.31		$1,017.6063	$1,017.60	$1,017.60	$1,017.50