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	$127.87	11.524%	$142.6057	$142.61	$142.60	$142.60
Purchase #2	$94.85	11.764%	$106.0082	$106.01	$106.00	$106.00
Purchase #3	$89.52	3.834%	$92.9522	$92.95	$92.95	$93.00
Purchase #4	$216.92	3.846%	$225.2627	$225.26	$225.25	$225.30
Purchase #5	$181.32	3.446%	$187.5683	$187.57	$187.55	$187.60
Purchase #6	$148.74	10.597%	$164.502	$164.50	$164.50	$164.50
Purchase #7	$148.79	4.281%	$155.1597	$155.16	$155.15	$155.20
7 purchase totals =	$1,008.01		$1,074.0588	$1,074.06	$1,074.00	$1,074.20