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	$242.87	10.793%	$269.083	$269.08	$269.10	$269.10
Purchase #2	$175.73	11.580%	$196.0795	$196.08	$196.10	$196.10
Purchase #3	$208.63	7.279%	$223.8162	$223.82	$223.80	$223.80
Purchase #4	$241.39	3.847%	$250.6763	$250.68	$250.70	$250.70
Purchase #5	$81.98	10.721%	$90.7691	$90.77	$90.75	$90.80
Purchase #6	$128.59	8.835%	$139.9509	$139.95	$139.95	$140.00
Purchase #7	$53.74	9.108%	$58.6346	$58.63	$58.65	$58.60
7 purchase totals =	$1,132.93		$1,229.0096	$1,229.01	$1,229.05	$1,229.10