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	$237.28	6.139%	$251.8466	$251.85	$251.85	$251.80
Purchase #2	$104.79	3.293%	$108.2407	$108.24	$108.25	$108.20
Purchase #3	$69.59	13.212%	$78.7842	$78.78	$78.80	$78.80
Purchase #4	$234.88	12.712%	$264.7379	$264.74	$264.75	$264.70
Purchase #5	$80.81	7.297%	$86.7067	$86.71	$86.70	$86.70
Purchase #6	$165.89	3.601%	$171.8637	$171.86	$171.85	$171.90
Purchase #7	$173.50	13.855%	$197.5384	$197.54	$197.55	$197.50
7 purchase totals =	$1,066.74		$1,159.7182	$1,159.72	$1,159.75	$1,159.60