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	$75.97	13.359%	$86.1188	$86.12	$86.10	$86.10
Purchase #2	$105.90	9.208%	$115.6513	$115.65	$115.65	$115.70
Purchase #3	$127.45	3.179%	$131.5016	$131.50	$131.50	$131.50
Purchase #4	$105.97	10.402%	$116.993	$116.99	$117.00	$117.00
Purchase #5	$167.83	13.819%	$191.0224	$191.02	$191.00	$191.00
Purchase #6	$19.97	9.543%	$21.8757	$21.88	$21.90	$21.90
Purchase #7	$33.40	11.111%	$37.1111	$37.11	$37.10	$37.10
7 purchase totals =	$636.49		$700.2739	$700.27	$700.25	$700.30