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	$51.31	9.192%	$56.0264	$56.03	$56.05	$56.00
Purchase #2	$61.50	6.393%	$65.4317	$65.43	$65.45	$65.40
Purchase #3	$97.44	6.217%	$103.4978	$103.50	$103.50	$103.50
Purchase #4	$141.76	8.153%	$153.3177	$153.32	$153.30	$153.30
Purchase #5	$238.69	10.769%	$264.3945	$264.39	$264.40	$264.40
Purchase #6	$200.35	10.289%	$220.964	$220.96	$220.95	$221.00
Purchase #7	$181.87	4.142%	$189.4031	$189.40	$189.40	$189.40
7 purchase totals =	$972.92		$1,053.0352	$1,053.03	$1,053.05	$1,053.00