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	$103.54	5.156%	$108.8785	$108.88	$108.90	$108.90
Purchase #2	$46.34	3.336%	$47.8859	$47.89	$47.90	$47.90
Purchase #3	$74.66	4.779%	$78.228	$78.23	$78.25	$78.20
Purchase #4	$238.41	13.612%	$270.8624	$270.86	$270.85	$270.90
Purchase #5	$67.38	7.863%	$72.6781	$72.68	$72.70	$72.70
Purchase #6	$62.73	10.582%	$69.3681	$69.37	$69.35	$69.40
Purchase #7	$234.48	12.638%	$264.1136	$264.11	$264.10	$264.10
7 purchase totals =	$827.54		$912.0146	$912.02	$912.05	$912.10