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	$81.94	12.219%	$91.9522	$91.95	$91.95	$92.00
Purchase #2	$86.71	6.338%	$92.2057	$92.21	$92.20	$92.20
Purchase #3	$178.83	6.393%	$190.2626	$190.26	$190.25	$190.30
Purchase #4	$109.30	8.336%	$118.4112	$118.41	$118.40	$118.40
Purchase #5	$53.54	7.315%	$57.4565	$57.46	$57.45	$57.50
Purchase #6	$153.56	8.571%	$166.7216	$166.72	$166.70	$166.70
Purchase #7	$250.69	4.416%	$261.7605	$261.76	$261.75	$261.80
7 purchase totals =	$914.57		$978.7703	$978.77	$978.70	$978.90