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	$189.75	3.321%	$196.0516	$196.05	$196.05	$196.10
Purchase #2	$35.90	11.483%	$40.0224	$40.02	$40.00	$40.00
Purchase #3	$42.88	5.616%	$45.2881	$45.29	$45.30	$45.30
Purchase #4	$178.32	9.270%	$194.8503	$194.85	$194.85	$194.90
Purchase #5	$18.90	11.325%	$21.0404	$21.04	$21.05	$21.00
Purchase #6	$235.46	9.582%	$258.0218	$258.02	$258.00	$258.00
Purchase #7	$67.58	4.354%	$70.5224	$70.52	$70.50	$70.50
7 purchase totals =	$768.79		$825.7970	$825.79	$825.75	$825.80