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	$215.82	3.566%	$223.5161	$223.52	$223.50	$223.50
Purchase #2	$128.30	3.801%	$133.1767	$133.18	$133.20	$133.20
Purchase #3	$150.90	6.606%	$160.8685	$160.87	$160.85	$160.90
Purchase #4	$159.93	11.333%	$178.0549	$178.05	$178.05	$178.10
Purchase #5	$158.78	9.705%	$174.1896	$174.19	$174.20	$174.20
Purchase #6	$127.25	6.177%	$135.1102	$135.11	$135.10	$135.10
Purchase #7	$81.58	9.145%	$89.0405	$89.04	$89.05	$89.00
7 purchase totals =	$1,022.56		$1,093.9565	$1,093.96	$1,093.95	$1,094.00