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	$226.43	7.346%	$243.0635	$243.06	$243.05	$243.10
Purchase #2	$19.42	3.561%	$20.1115	$20.11	$20.10	$20.10
Purchase #3	$246.69	13.625%	$280.3015	$280.30	$280.30	$280.30
Purchase #4	$152.31	6.704%	$162.5209	$162.52	$162.50	$162.50
Purchase #5	$121.80	9.813%	$133.7522	$133.75	$133.75	$133.80
Purchase #6	$205.48	11.396%	$228.8965	$228.90	$228.90	$228.90
Purchase #7	$104.40	6.413%	$111.0952	$111.10	$111.10	$111.10
7 purchase totals =	$1,076.53		$1,179.7413	$1,179.74	$1,179.70	$1,179.80