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	$131.48	8.693%	$142.9096	$142.91	$142.90	$142.90
Purchase #2	$37.81	6.599%	$40.3051	$40.31	$40.30	$40.30
Purchase #3	$133.27	6.363%	$141.75	$141.75	$141.75	$141.80
Purchase #4	$167.29	11.519%	$186.5601	$186.56	$186.55	$186.60
Purchase #5	$115.81	13.333%	$131.2509	$131.25	$131.25	$131.30
Purchase #6	$210.56	6.187%	$223.5873	$223.59	$223.60	$223.60
Purchase #7	$201.44	11.773%	$225.1555	$225.16	$225.15	$225.20
7 purchase totals =	$997.66		$1,091.5185	$1,091.53	$1,091.50	$1,091.70