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	$62.50	13.691%	$71.0569	$71.06	$71.05	$71.10
Purchase #2	$237.40	12.673%	$267.4857	$267.49	$267.50	$267.50
Purchase #3	$85.89	4.145%	$89.4501	$89.45	$89.45	$89.50
Purchase #4	$46.75	13.497%	$53.0598	$53.06	$53.05	$53.10
Purchase #5	$163.93	6.216%	$174.1199	$174.12	$174.10	$174.10
Purchase #6	$174.31	12.461%	$196.0308	$196.03	$196.05	$196.00
Purchase #7	$166.90	7.312%	$179.1037	$179.10	$179.10	$179.10
7 purchase totals =	$937.68		$1,030.3069	$1,030.31	$1,030.30	$1,030.40