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	$172.44	11.244%	$191.8292	$191.83	$191.85	$191.80
Purchase #2	$70.80	6.719%	$75.5571	$75.56	$75.55	$75.60
Purchase #3	$69.72	12.444%	$78.396	$78.40	$78.40	$78.40
Purchase #4	$20.26	12.632%	$22.8192	$22.82	$22.80	$22.80
Purchase #5	$68.25	3.712%	$70.7834	$70.78	$70.80	$70.80
Purchase #6	$211.66	8.574%	$229.8077	$229.81	$229.80	$229.80
Purchase #7	$89.91	9.868%	$98.7823	$98.78	$98.80	$98.80
7 purchase totals =	$703.04		$767.9749	$767.98	$768.00	$768.00