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	$170.47	12.844%	$192.3652	$192.37	$192.35	$192.40
Purchase #2	$242.64	11.864%	$271.4268	$271.43	$271.45	$271.40
Purchase #3	$225.46	6.729%	$240.6312	$240.63	$240.65	$240.60
Purchase #4	$27.90	5.717%	$29.495	$29.50	$29.50	$29.50
Purchase #5	$168.54	11.798%	$188.4243	$188.42	$188.40	$188.40
Purchase #6	$31.52	12.551%	$35.4761	$35.48	$35.50	$35.50
Purchase #7	$88.69	5.724%	$93.7666	$93.77	$93.75	$93.80
7 purchase totals =	$955.22		$1,051.5852	$1,051.60	$1,051.60	$1,051.60