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	$58.37	9.822%	$64.1031	$64.10	$64.10	$64.10
Purchase #2	$45.65	12.606%	$51.4046	$51.40	$51.40	$51.40
Purchase #3	$200.36	13.102%	$226.6112	$226.61	$226.60	$226.60
Purchase #4	$88.40	13.637%	$100.4551	$100.46	$100.45	$100.50
Purchase #5	$179.37	7.231%	$192.3402	$192.34	$192.35	$192.30
Purchase #6	$210.33	5.721%	$222.363	$222.36	$222.35	$222.40
Purchase #7	$197.46	12.494%	$222.1307	$222.13	$222.15	$222.10
7 purchase totals =	$979.94		$1,079.4079	$1,079.40	$1,079.40	$1,079.40