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	$68.63	3.669%	$71.148	$71.15	$71.15	$71.10
Purchase #2	$156.83	7.632%	$168.7993	$168.80	$168.80	$168.80
Purchase #3	$39.52	10.162%	$43.536	$43.54	$43.55	$43.50
Purchase #4	$230.44	4.819%	$241.5449	$241.54	$241.55	$241.50
Purchase #5	$221.56	5.149%	$232.9681	$232.97	$232.95	$233.00
Purchase #6	$88.83	8.834%	$96.6772	$96.68	$96.70	$96.70
Purchase #7	$234.42	6.342%	$249.2869	$249.29	$249.30	$249.30
7 purchase totals =	$1,040.23		$1,103.9604	$1,103.97	$1,104.00	$1,103.90