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	$201.25	6.118%	$213.5625	$213.56	$213.55	$213.60
Purchase #2	$36.85	3.218%	$38.0358	$38.04	$38.05	$38.00
Purchase #3	$126.89	4.839%	$133.0302	$133.03	$133.05	$133.00
Purchase #4	$187.41	4.748%	$196.3082	$196.31	$196.30	$196.30
Purchase #5	$219.53	12.731%	$247.4784	$247.48	$247.50	$247.50
Purchase #6	$76.55	7.820%	$82.5362	$82.54	$82.55	$82.50
Purchase #7	$81.46	9.490%	$89.1906	$89.19	$89.20	$89.20
7 purchase totals =	$929.94		$1,000.1419	$1,000.15	$1,000.20	$1,000.10