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	$215.77	5.708%	$228.0862	$228.09	$228.10	$228.10
Purchase #2	$100.82	4.370%	$105.2258	$105.23	$105.25	$105.20
Purchase #3	$131.84	3.435%	$136.3687	$136.37	$136.35	$136.40
Purchase #4	$99.44	6.229%	$105.6341	$105.63	$105.65	$105.60
Purchase #5	$98.71	5.194%	$103.837	$103.84	$103.85	$103.80
Purchase #6	$250.36	11.296%	$278.6407	$278.64	$278.65	$278.60
Purchase #7	$166.37	13.618%	$189.0263	$189.03	$189.05	$189.00
7 purchase totals =	$1,063.31		$1,146.8188	$1,146.83	$1,146.90	$1,146.70