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	$61.73	9.333%	$67.4913	$67.49	$67.50	$67.50
Purchase #2	$148.74	7.688%	$160.1751	$160.18	$160.20	$160.20
Purchase #3	$178.94	3.582%	$185.3496	$185.35	$185.35	$185.30
Purchase #4	$167.96	13.755%	$191.0629	$191.06	$191.05	$191.10
Purchase #5	$94.28	7.139%	$101.0106	$101.01	$101.00	$101.00
Purchase #6	$165.31	8.396%	$179.1894	$179.19	$179.20	$179.20
Purchase #7	$243.43	6.206%	$258.5373	$258.54	$258.55	$258.50
7 purchase totals =	$1,060.39		$1,142.8162	$1,142.82	$1,142.85	$1,142.80