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	$172.44	8.142%	$186.4801	$186.48	$186.50	$186.50
Purchase #2	$207.45	6.789%	$221.5338	$221.53	$221.55	$221.50
Purchase #3	$119.46	10.225%	$131.6748	$131.67	$131.65	$131.70
Purchase #4	$122.46	8.714%	$133.1312	$133.13	$133.15	$133.10
Purchase #5	$134.82	11.786%	$150.7099	$150.71	$150.70	$150.70
Purchase #6	$239.53	4.562%	$250.4574	$250.46	$250.45	$250.50
Purchase #7	$94.33	10.318%	$104.063	$104.06	$104.05	$104.10
7 purchase totals =	$1,090.49		$1,178.0502	$1,178.04	$1,178.05	$1,178.10