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	$101.57	4.336%	$105.9741	$105.97	$105.95	$106.00
Purchase #2	$139.56	7.235%	$149.6572	$149.66	$149.65	$149.70
Purchase #3	$205.53	4.471%	$214.7192	$214.72	$214.70	$214.70
Purchase #4	$187.98	13.829%	$213.9758	$213.98	$214.00	$214.00
Purchase #5	$96.49	13.435%	$109.4534	$109.45	$109.45	$109.50
Purchase #6	$82.71	8.871%	$90.0472	$90.05	$90.05	$90.00
Purchase #7	$124.66	5.219%	$131.166	$131.17	$131.15	$131.20
7 purchase totals =	$938.50		$1,014.9929	$1,015.00	$1,014.95	$1,015.10