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	$188.83	13.473%	$214.2711	$214.27	$214.25	$214.30
Purchase #2	$205.40	5.652%	$217.0092	$217.01	$217.00	$217.00
Purchase #3	$90.87	3.811%	$94.3331	$94.33	$94.35	$94.30
Purchase #4	$60.67	11.868%	$67.8703	$67.87	$67.85	$67.90
Purchase #5	$165.76	9.264%	$181.116	$181.12	$181.10	$181.10
Purchase #6	$137.34	7.306%	$147.3741	$147.37	$147.35	$147.40
Purchase #7	$222.83	9.172%	$243.268	$243.27	$243.25	$243.30
7 purchase totals =	$1,071.70		$1,165.2418	$1,165.24	$1,165.15	$1,165.30