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	$49.48	9.182%	$54.0233	$54.02	$54.00	$54.00
Purchase #2	$188.88	11.172%	$209.9817	$209.98	$210.00	$210.00
Purchase #3	$102.65	10.796%	$113.7321	$113.73	$113.75	$113.70
Purchase #4	$165.35	8.618%	$179.5999	$179.60	$179.60	$179.60
Purchase #5	$184.93	3.132%	$190.722	$190.72	$190.70	$190.70
Purchase #6	$167.93	6.431%	$178.7296	$178.73	$178.75	$178.70
Purchase #7	$86.94	13.596%	$98.7604	$98.76	$98.75	$98.80
7 purchase totals =	$946.16		$1,025.5490	$1,025.54	$1,025.55	$1,025.50