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	$86.29	7.459%	$92.7264	$92.73	$92.75	$92.70
Purchase #2	$131.87	13.832%	$150.1103	$150.11	$150.10	$150.10
Purchase #3	$247.63	13.214%	$280.3518	$280.35	$280.35	$280.40
Purchase #4	$47.93	9.769%	$52.6123	$52.61	$52.60	$52.60
Purchase #5	$213.48	4.168%	$222.3778	$222.38	$222.40	$222.40
Purchase #6	$131.56	12.748%	$148.3313	$148.33	$148.35	$148.30
Purchase #7	$71.90	4.826%	$75.3699	$75.37	$75.35	$75.40
7 purchase totals =	$930.66		$1,021.8798	$1,021.88	$1,021.90	$1,021.90