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	$163.68	6.623%	$174.5205	$174.52	$174.50	$174.50
Purchase #2	$173.38	6.711%	$185.0155	$185.02	$185.00	$185.00
Purchase #3	$57.42	7.758%	$61.8746	$61.87	$61.85	$61.90
Purchase #4	$162.49	11.124%	$180.5654	$180.57	$180.55	$180.60
Purchase #5	$183.70	9.286%	$200.7584	$200.76	$200.75	$200.80
Purchase #6	$22.84	8.347%	$24.7465	$24.75	$24.75	$24.70
Purchase #7	$133.71	12.760%	$150.7714	$150.77	$150.75	$150.80
7 purchase totals =	$897.22		$978.2523	$978.26	$978.15	$978.30