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	$173.74	5.243%	$182.8492	$182.85	$182.85	$182.80
Purchase #2	$84.98	5.510%	$89.6624	$89.66	$89.65	$89.70
Purchase #3	$72.69	11.192%	$80.8255	$80.83	$80.85	$80.80
Purchase #4	$168.97	10.532%	$186.7659	$186.77	$186.75	$186.80
Purchase #5	$50.36	7.482%	$54.1279	$54.13	$54.15	$54.10
Purchase #6	$133.73	5.805%	$141.493	$141.49	$141.50	$141.50
Purchase #7	$240.91	6.416%	$256.3668	$256.37	$256.35	$256.40
7 purchase totals =	$925.38		$992.0907	$992.10	$992.10	$992.10