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	$97.59	7.137%	$104.555	$104.56	$104.55	$104.60
Purchase #2	$195.32	4.352%	$203.8203	$203.82	$203.80	$203.80
Purchase #3	$80.66	13.130%	$91.2507	$91.25	$91.25	$91.30
Purchase #4	$85.57	12.324%	$96.1156	$96.12	$96.10	$96.10
Purchase #5	$138.37	4.674%	$144.8374	$144.84	$144.85	$144.80
Purchase #6	$116.54	9.768%	$127.9236	$127.92	$127.90	$127.90
Purchase #7	$67.34	10.516%	$74.4215	$74.42	$74.40	$74.40
7 purchase totals =	$781.39		$842.9241	$842.93	$842.85	$842.90