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	$99.69	4.250%	$103.9268	$103.93	$103.95	$103.90
Purchase #2	$39.55	3.735%	$41.0272	$41.03	$41.05	$41.00
Purchase #3	$89.32	8.558%	$96.964	$96.96	$96.95	$97.00
Purchase #4	$152.26	10.233%	$167.8408	$167.84	$167.85	$167.80
Purchase #5	$139.74	10.791%	$154.8193	$154.82	$154.80	$154.80
Purchase #6	$166.64	3.402%	$172.3091	$172.31	$172.30	$172.30
Purchase #7	$246.79	13.139%	$279.2157	$279.22	$279.20	$279.20
7 purchase totals =	$933.99		$1,016.1029	$1,016.11	$1,016.10	$1,016.00