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	$92.38	8.120%	$99.8813	$99.88	$99.90	$99.90
Purchase #2	$194.85	9.114%	$212.6086	$212.61	$212.60	$212.60
Purchase #3	$54.36	5.557%	$57.3808	$57.38	$57.40	$57.40
Purchase #4	$66.40	9.401%	$72.6423	$72.64	$72.65	$72.60
Purchase #5	$68.93	10.717%	$76.3172	$76.32	$76.30	$76.30
Purchase #6	$156.57	5.337%	$164.9261	$164.93	$164.95	$164.90
Purchase #7	$84.66	13.532%	$96.1162	$96.12	$96.10	$96.10
7 purchase totals =	$718.15		$779.8725	$779.88	$779.90	$779.80