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	$238.40	12.533%	$268.2787	$268.28	$268.30	$268.30
Purchase #2	$54.81	9.234%	$59.8712	$59.87	$59.85	$59.90
Purchase #3	$247.27	7.684%	$266.2702	$266.27	$266.25	$266.30
Purchase #4	$220.30	9.708%	$241.6867	$241.69	$241.70	$241.70
Purchase #5	$102.74	7.684%	$110.6345	$110.63	$110.65	$110.60
Purchase #6	$112.59	6.526%	$119.9376	$119.94	$119.95	$119.90
Purchase #7	$71.30	7.793%	$76.8564	$76.86	$76.85	$76.90
7 purchase totals =	$1,047.41		$1,143.5353	$1,143.54	$1,143.55	$1,143.60