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	$205.98	9.528%	$225.6058	$225.61	$225.60	$225.60
Purchase #2	$194.54	9.780%	$213.566	$213.57	$213.55	$213.60
Purchase #3	$223.96	8.440%	$242.8622	$242.86	$242.85	$242.90
Purchase #4	$25.87	8.501%	$28.0692	$28.07	$28.05	$28.10
Purchase #5	$248.50	6.553%	$264.7842	$264.78	$264.80	$264.80
Purchase #6	$48.40	9.308%	$52.9051	$52.91	$52.90	$52.90
Purchase #7	$116.85	12.489%	$131.4434	$131.44	$131.45	$131.40
7 purchase totals =	$1,064.10		$1,159.2359	$1,159.24	$1,159.20	$1,159.30