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	$158.83	9.755%	$174.3239	$174.32	$174.30	$174.30
Purchase #2	$169.79	12.676%	$191.3126	$191.31	$191.30	$191.30
Purchase #3	$71.38	10.595%	$78.9427	$78.94	$78.95	$78.90
Purchase #4	$74.37	8.639%	$80.7948	$80.79	$80.80	$80.80
Purchase #5	$239.70	11.642%	$267.6059	$267.61	$267.60	$267.60
Purchase #6	$96.77	5.292%	$101.8911	$101.89	$101.90	$101.90
Purchase #7	$11.60	9.335%	$12.6829	$12.68	$12.70	$12.70
7 purchase totals =	$822.44		$907.5539	$907.54	$907.55	$907.50