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	$98.50	12.357%	$110.6716	$110.67	$110.65	$110.70
Purchase #2	$115.38	10.782%	$127.8203	$127.82	$127.80	$127.80
Purchase #3	$85.86	9.727%	$94.2116	$94.21	$94.20	$94.20
Purchase #4	$71.35	11.666%	$79.6737	$79.67	$79.65	$79.70
Purchase #5	$78.31	9.130%	$85.4597	$85.46	$85.45	$85.50
Purchase #6	$27.47	12.338%	$30.8592	$30.86	$30.85	$30.90
Purchase #7	$45.55	3.710%	$47.2399	$47.24	$47.25	$47.20
7 purchase totals =	$522.42		$575.9360	$575.93	$575.85	$576.00