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	$37.97	7.838%	$40.9461	$40.95	$40.95	$40.90
Purchase #2	$243.50	12.716%	$274.4635	$274.46	$274.45	$274.50
Purchase #3	$82.98	8.288%	$89.8574	$89.86	$89.85	$89.90
Purchase #4	$204.83	3.810%	$212.634	$212.63	$212.65	$212.60
Purchase #5	$150.76	7.492%	$162.0549	$162.05	$162.05	$162.10
Purchase #6	$176.75	12.608%	$199.0346	$199.03	$199.05	$199.00
Purchase #7	$153.90	13.170%	$174.1686	$174.17	$174.15	$174.20
7 purchase totals =	$1,050.69		$1,153.1591	$1,153.15	$1,153.15	$1,153.20