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	$237.39	13.516%	$269.4756	$269.48	$269.50	$269.50
Purchase #2	$222.31	12.140%	$249.2984	$249.30	$249.30	$249.30
Purchase #3	$42.76	4.729%	$44.7821	$44.78	$44.80	$44.80
Purchase #4	$101.26	4.323%	$105.6375	$105.64	$105.65	$105.60
Purchase #5	$35.25	5.427%	$37.163	$37.16	$37.15	$37.20
Purchase #6	$71.91	9.233%	$78.5495	$78.55	$78.55	$78.50
Purchase #7	$86.39	11.819%	$96.6004	$96.60	$96.60	$96.60
7 purchase totals =	$797.27		$881.5065	$881.51	$881.55	$881.50