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	$127.78	9.658%	$140.121	$140.12	$140.10	$140.10
Purchase #2	$21.90	7.173%	$23.4709	$23.47	$23.45	$23.50
Purchase #3	$211.50	9.287%	$231.142	$231.14	$231.15	$231.10
Purchase #4	$142.53	9.604%	$156.2186	$156.22	$156.20	$156.20
Purchase #5	$89.35	11.524%	$99.6467	$99.65	$99.65	$99.60
Purchase #6	$48.35	4.834%	$50.6872	$50.69	$50.70	$50.70
Purchase #7	$181.76	9.636%	$199.2744	$199.27	$199.25	$199.30
7 purchase totals =	$823.17		$900.5608	$900.56	$900.50	$900.50