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	$49.53	8.530%	$53.7549	$53.75	$53.75	$53.80
Purchase #2	$127.76	12.399%	$143.601	$143.60	$143.60	$143.60
Purchase #3	$107.54	4.173%	$112.0276	$112.03	$112.05	$112.00
Purchase #4	$130.39	5.428%	$137.4676	$137.47	$137.45	$137.50
Purchase #5	$128.88	10.188%	$142.0103	$142.01	$142.00	$142.00
Purchase #6	$118.98	11.421%	$132.5687	$132.57	$132.55	$132.60
Purchase #7	$249.34	9.854%	$273.91	$273.91	$273.90	$273.90
7 purchase totals =	$912.42		$995.3401	$995.34	$995.30	$995.40