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	$56.80	9.148%	$61.9961	$62.00	$62.00	$62.00
Purchase #2	$41.52	6.555%	$44.2416	$44.24	$44.25	$44.20
Purchase #3	$80.58	11.490%	$89.8386	$89.84	$89.85	$89.80
Purchase #4	$216.97	11.767%	$242.5009	$242.50	$242.50	$242.50
Purchase #5	$153.93	11.648%	$171.8598	$171.86	$171.85	$171.90
Purchase #6	$174.65	3.824%	$181.3286	$181.33	$181.35	$181.30
Purchase #7	$140.35	8.583%	$152.3962	$152.40	$152.40	$152.40
7 purchase totals =	$864.80		$944.1618	$944.17	$944.20	$944.10