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	$167.91	9.656%	$184.1234	$184.12	$184.10	$184.10
Purchase #2	$101.88	7.443%	$109.4629	$109.46	$109.45	$109.50
Purchase #3	$123.34	3.223%	$127.3152	$127.32	$127.30	$127.30
Purchase #4	$159.60	12.140%	$178.9754	$178.98	$179.00	$179.00
Purchase #5	$237.68	3.137%	$245.136	$245.14	$245.15	$245.10
Purchase #6	$189.56	12.762%	$213.7516	$213.75	$213.75	$213.80
Purchase #7	$189.91	7.310%	$203.7924	$203.79	$203.80	$203.80
7 purchase totals =	$1,169.88		$1,262.5569	$1,262.56	$1,262.55	$1,262.60