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	$130.61	10.710%	$144.5983	$144.60	$144.60	$144.60
Purchase #2	$179.41	9.736%	$196.8774	$196.88	$196.90	$196.90
Purchase #3	$133.71	6.173%	$141.9639	$141.96	$141.95	$142.00
Purchase #4	$24.54	4.629%	$25.676	$25.68	$25.70	$25.70
Purchase #5	$60.46	3.776%	$62.743	$62.74	$62.75	$62.70
Purchase #6	$203.95	4.384%	$212.8912	$212.89	$212.90	$212.90
Purchase #7	$248.65	13.393%	$281.9517	$281.95	$281.95	$282.00
7 purchase totals =	$981.33		$1,066.7015	$1,066.70	$1,066.75	$1,066.80