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	$204.64	8.731%	$222.5071	$222.51	$222.50	$222.50
Purchase #2	$34.82	8.154%	$37.6592	$37.66	$37.65	$37.70
Purchase #3	$193.80	10.399%	$213.9533	$213.95	$213.95	$214.00
Purchase #4	$240.56	9.692%	$263.8751	$263.88	$263.90	$263.90
Purchase #5	$51.36	11.221%	$57.1231	$57.12	$57.10	$57.10
Purchase #6	$235.36	11.662%	$262.8077	$262.81	$262.80	$262.80
Purchase #7	$39.36	7.192%	$42.1908	$42.19	$42.20	$42.20
7 purchase totals =	$999.90		$1,100.1163	$1,100.12	$1,100.10	$1,100.20