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	$68.52	13.623%	$77.8545	$77.85	$77.85	$77.90
Purchase #2	$91.75	13.464%	$104.1032	$104.10	$104.10	$104.10
Purchase #3	$249.98	12.609%	$281.5	$281.50	$281.50	$281.50
Purchase #4	$59.40	12.650%	$66.9141	$66.91	$66.90	$66.90
Purchase #5	$79.43	11.822%	$88.8202	$88.82	$88.80	$88.80
Purchase #6	$190.37	7.309%	$204.2841	$204.28	$204.30	$204.30
Purchase #7	$73.31	7.667%	$78.9307	$78.93	$78.95	$78.90
7 purchase totals =	$812.76		$902.4068	$902.39	$902.40	$902.40