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	$182.42	6.413%	$194.1186	$194.12	$194.10	$194.10
Purchase #2	$94.43	5.552%	$99.6728	$99.67	$99.65	$99.70
Purchase #3	$61.32	11.636%	$68.4552	$68.46	$68.45	$68.50
Purchase #4	$63.50	13.697%	$72.1976	$72.20	$72.20	$72.20
Purchase #5	$128.38	4.511%	$134.1712	$134.17	$134.15	$134.20
Purchase #6	$78.76	4.544%	$82.3389	$82.34	$82.35	$82.30
Purchase #7	$123.97	7.347%	$133.0781	$133.08	$133.10	$133.10
7 purchase totals =	$732.78		$784.0324	$784.04	$784.00	$784.10