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	$247.73	10.584%	$273.9497	$273.95	$273.95	$273.90
Purchase #2	$231.84	4.823%	$243.0216	$243.02	$243.00	$243.00
Purchase #3	$91.33	5.696%	$96.5322	$96.53	$96.55	$96.50
Purchase #4	$24.44	5.798%	$25.857	$25.86	$25.85	$25.90
Purchase #5	$242.92	8.424%	$263.3836	$263.38	$263.40	$263.40
Purchase #6	$11.34	12.624%	$12.7716	$12.77	$12.75	$12.80
Purchase #7	$90.94	11.400%	$101.3072	$101.31	$101.30	$101.30
7 purchase totals =	$940.54		$1,016.8229	$1,016.82	$1,016.80	$1,016.80