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	$70.39	3.345%	$72.7445	$72.74	$72.75	$72.70
Purchase #2	$197.98	9.118%	$216.0318	$216.03	$216.05	$216.00
Purchase #3	$84.53	6.874%	$90.3406	$90.34	$90.35	$90.30
Purchase #4	$165.82	3.592%	$171.7763	$171.78	$171.80	$171.80
Purchase #5	$80.55	6.363%	$85.6754	$85.68	$85.70	$85.70
Purchase #6	$90.28	4.819%	$94.6306	$94.63	$94.65	$94.60
Purchase #7	$238.54	13.106%	$269.8031	$269.80	$269.80	$269.80
7 purchase totals =	$928.09		$1,001.0023	$1,001.00	$1,001.10	$1,000.90