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	$43.34	6.524%	$46.1675	$46.17	$46.15	$46.20
Purchase #2	$54.72	13.454%	$62.082	$62.08	$62.10	$62.10
Purchase #3	$181.46	3.627%	$188.0416	$188.04	$188.05	$188.00
Purchase #4	$71.84	6.493%	$76.5046	$76.50	$76.50	$76.50
Purchase #5	$100.56	10.483%	$111.1017	$111.10	$111.10	$111.10
Purchase #6	$165.68	11.178%	$184.1997	$184.20	$184.20	$184.20
Purchase #7	$167.66	13.259%	$189.89	$189.89	$189.90	$189.90
7 purchase totals =	$785.26		$857.9871	$857.98	$858.00	$858.00