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	$169.43	7.740%	$182.5439	$182.54	$182.55	$182.50
Purchase #2	$153.65	5.794%	$162.5525	$162.55	$162.55	$162.60
Purchase #3	$102.89	9.240%	$112.397	$112.40	$112.40	$112.40
Purchase #4	$26.77	12.201%	$30.0362	$30.04	$30.05	$30.00
Purchase #5	$55.93	7.122%	$59.9133	$59.91	$59.90	$59.90
Purchase #6	$156.58	11.679%	$174.867	$174.87	$174.85	$174.90
Purchase #7	$173.86	9.858%	$190.9991	$191.00	$191.00	$191.00
7 purchase totals =	$839.11		$913.3090	$913.31	$913.30	$913.30