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	$88.43	6.613%	$94.2779	$94.28	$94.30	$94.30
Purchase #2	$47.86	8.608%	$51.9798	$51.98	$52.00	$52.00
Purchase #3	$88.94	9.414%	$97.3128	$97.31	$97.30	$97.30
Purchase #4	$227.81	5.598%	$240.5628	$240.56	$240.55	$240.60
Purchase #5	$188.33	10.664%	$208.4135	$208.41	$208.40	$208.40
Purchase #6	$34.40	10.202%	$37.9095	$37.91	$37.90	$37.90
Purchase #7	$250.82	12.661%	$282.5763	$282.58	$282.60	$282.60
7 purchase totals =	$926.59		$1,013.0326	$1,013.03	$1,013.05	$1,013.10