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	$53.36	12.709%	$60.1415	$60.14	$60.15	$60.10
Purchase #2	$219.91	12.133%	$246.5917	$246.59	$246.60	$246.60
Purchase #3	$202.78	4.373%	$211.6476	$211.65	$211.65	$211.60
Purchase #4	$211.91	4.718%	$221.9079	$221.91	$221.90	$221.90
Purchase #5	$109.82	3.248%	$113.387	$113.39	$113.40	$113.40
Purchase #6	$116.45	12.792%	$131.3463	$131.35	$131.35	$131.30
Purchase #7	$102.43	6.674%	$109.2662	$109.27	$109.25	$109.30
7 purchase totals =	$1,016.66		$1,094.2882	$1,094.30	$1,094.30	$1,094.20