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	$152.56	11.364%	$169.8969	$169.90	$169.90	$169.90
Purchase #2	$246.52	13.719%	$280.3401	$280.34	$280.35	$280.30
Purchase #3	$55.82	5.764%	$59.0375	$59.04	$59.05	$59.00
Purchase #4	$196.60	7.404%	$211.1563	$211.16	$211.15	$211.20
Purchase #5	$170.40	12.855%	$192.3049	$192.30	$192.30	$192.30
Purchase #6	$228.97	8.550%	$248.5469	$248.55	$248.55	$248.50
Purchase #7	$249.95	12.447%	$281.0613	$281.06	$281.05	$281.10
7 purchase totals =	$1,300.82		$1,442.3439	$1,442.35	$1,442.35	$1,442.30