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	$55.86	4.830%	$58.558	$58.56	$58.55	$58.60
Purchase #2	$70.66	11.726%	$78.9456	$78.95	$78.95	$78.90
Purchase #3	$47.66	12.338%	$53.5403	$53.54	$53.55	$53.50
Purchase #4	$187.98	13.336%	$213.049	$213.05	$213.05	$213.00
Purchase #5	$92.48	10.428%	$102.1238	$102.12	$102.10	$102.10
Purchase #6	$145.29	10.194%	$160.1009	$160.10	$160.10	$160.10
Purchase #7	$249.85	5.174%	$262.7772	$262.78	$262.80	$262.80
7 purchase totals =	$849.78		$929.0948	$929.10	$929.10	$929.00