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	$112.60	13.183%	$127.4441	$127.44	$127.45	$127.40
Purchase #2	$80.87	6.850%	$86.4096	$86.41	$86.40	$86.40
Purchase #3	$157.98	13.648%	$179.5411	$179.54	$179.55	$179.50
Purchase #4	$179.79	6.215%	$190.9639	$190.96	$190.95	$191.00
Purchase #5	$131.74	6.781%	$140.6733	$140.67	$140.65	$140.70
Purchase #6	$168.25	13.359%	$190.7265	$190.73	$190.75	$190.70
Purchase #7	$219.92	11.139%	$244.4169	$244.42	$244.40	$244.40
7 purchase totals =	$1,051.15		$1,160.1754	$1,160.17	$1,160.15	$1,160.10