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	$75.41	8.849%	$82.083	$82.08	$82.10	$82.10
Purchase #2	$234.78	8.552%	$254.8584	$254.86	$254.85	$254.90
Purchase #3	$229.98	11.430%	$256.2667	$256.27	$256.25	$256.30
Purchase #4	$132.59	8.326%	$143.6294	$143.63	$143.65	$143.60
Purchase #5	$163.37	9.142%	$178.3053	$178.31	$178.30	$178.30
Purchase #6	$234.29	4.617%	$245.1072	$245.11	$245.10	$245.10
Purchase #7	$37.85	11.263%	$42.113	$42.11	$42.10	$42.10
7 purchase totals =	$1,108.27		$1,202.3630	$1,202.37	$1,202.35	$1,202.40