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	$67.26	7.260%	$72.1431	$72.14	$72.15	$72.10
Purchase #2	$52.91	9.102%	$57.7259	$57.73	$57.75	$57.70
Purchase #3	$116.35	12.674%	$131.0962	$131.10	$131.10	$131.10
Purchase #4	$180.39	8.109%	$195.0178	$195.02	$195.00	$195.00
Purchase #5	$72.85	7.736%	$78.4857	$78.49	$78.50	$78.50
Purchase #6	$30.81	5.452%	$32.4898	$32.49	$32.50	$32.50
Purchase #7	$239.25	12.360%	$268.8213	$268.82	$268.80	$268.80
7 purchase totals =	$759.82		$835.7798	$835.79	$835.80	$835.70