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	$82.69	8.396%	$89.6327	$89.63	$89.65	$89.60
Purchase #2	$53.87	7.519%	$57.9205	$57.92	$57.90	$57.90
Purchase #3	$168.76	3.233%	$174.216	$174.22	$174.20	$174.20
Purchase #4	$146.68	12.515%	$165.037	$165.04	$165.05	$165.00
Purchase #5	$219.42	12.474%	$246.7905	$246.79	$246.80	$246.80
Purchase #6	$136.74	13.364%	$155.0139	$155.01	$155.00	$155.00
Purchase #7	$142.32	7.209%	$152.5798	$152.58	$152.60	$152.60
7 purchase totals =	$950.48		$1,041.1904	$1,041.19	$1,041.20	$1,041.10