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	$197.45	8.178%	$213.5975	$213.60	$213.60	$213.60
Purchase #2	$88.62	12.108%	$99.3501	$99.35	$99.35	$99.40
Purchase #3	$157.69	11.134%	$175.2472	$175.25	$175.25	$175.20
Purchase #4	$79.61	7.270%	$85.3976	$85.40	$85.40	$85.40
Purchase #5	$60.58	12.143%	$67.9362	$67.94	$67.95	$67.90
Purchase #6	$156.50	11.665%	$174.7557	$174.76	$174.75	$174.80
Purchase #7	$96.57	13.279%	$109.3935	$109.39	$109.40	$109.40
7 purchase totals =	$837.02		$925.6778	$925.69	$925.70	$925.70