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	$115.27	8.492%	$125.0587	$125.06	$125.05	$125.10
Purchase #2	$164.76	7.118%	$176.4876	$176.49	$176.50	$176.50
Purchase #3	$85.40	4.599%	$89.3275	$89.33	$89.35	$89.30
Purchase #4	$109.43	12.854%	$123.4961	$123.50	$123.50	$123.50
Purchase #5	$195.58	8.460%	$212.1261	$212.13	$212.15	$212.10
Purchase #6	$191.75	6.816%	$204.8197	$204.82	$204.80	$204.80
Purchase #7	$27.65	12.517%	$31.111	$31.11	$31.10	$31.10
7 purchase totals =	$889.84		$962.4267	$962.44	$962.45	$962.40