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	$139.34	3.653%	$144.4301	$144.43	$144.45	$144.40
Purchase #2	$234.30	10.606%	$259.1499	$259.15	$259.15	$259.10
Purchase #3	$250.74	5.794%	$265.2679	$265.27	$265.25	$265.30
Purchase #4	$73.88	7.684%	$79.5569	$79.56	$79.55	$79.60
Purchase #5	$68.91	13.684%	$78.3396	$78.34	$78.35	$78.30
Purchase #6	$218.89	11.523%	$244.1127	$244.11	$244.10	$244.10
Purchase #7	$174.95	9.710%	$191.9376	$191.94	$191.95	$191.90
7 purchase totals =	$1,161.01		$1,262.7947	$1,262.80	$1,262.80	$1,262.70