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	$73.25	7.379%	$78.6551	$78.66	$78.65	$78.70
Purchase #2	$102.41	6.809%	$109.3831	$109.38	$109.40	$109.40
Purchase #3	$76.79	13.174%	$86.9063	$86.91	$86.90	$86.90
Purchase #4	$75.29	6.592%	$80.2531	$80.25	$80.25	$80.30
Purchase #5	$242.56	5.390%	$255.634	$255.63	$255.65	$255.60
Purchase #6	$107.93	6.851%	$115.3243	$115.32	$115.30	$115.30
Purchase #7	$150.69	13.833%	$171.5349	$171.53	$171.55	$171.50
7 purchase totals =	$828.92		$897.6908	$897.68	$897.70	$897.70