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	$120.43	11.792%	$134.6311	$134.63	$134.65	$134.60
Purchase #2	$82.93	7.600%	$89.2327	$89.23	$89.25	$89.20
Purchase #3	$68.25	4.174%	$71.0988	$71.10	$71.10	$71.10
Purchase #4	$140.54	7.118%	$150.5436	$150.54	$150.55	$150.50
Purchase #5	$232.82	12.136%	$261.075	$261.08	$261.10	$261.10
Purchase #6	$160.78	8.861%	$175.0267	$175.03	$175.05	$175.00
Purchase #7	$234.56	3.792%	$243.4545	$243.45	$243.45	$243.50
7 purchase totals =	$1,040.31		$1,125.0624	$1,125.06	$1,125.15	$1,125.00