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	$41.51	7.311%	$44.5448	$44.54	$44.55	$44.50
Purchase #2	$90.41	13.815%	$102.9001	$102.90	$102.90	$102.90
Purchase #3	$230.59	6.388%	$245.3201	$245.32	$245.30	$245.30
Purchase #4	$250.81	11.793%	$280.388	$280.39	$280.40	$280.40
Purchase #5	$78.55	6.743%	$83.8466	$83.85	$83.85	$83.80
Purchase #6	$249.31	6.665%	$265.9265	$265.93	$265.95	$265.90
Purchase #7	$44.54	7.288%	$47.7861	$47.79	$47.80	$47.80
7 purchase totals =	$985.72		$1,070.7122	$1,070.72	$1,070.75	$1,070.60