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	$212.36	9.229%	$231.9587	$231.96	$231.95	$232.00
Purchase #2	$156.78	7.817%	$169.0355	$169.04	$169.05	$169.00
Purchase #3	$104.92	4.123%	$109.2459	$109.25	$109.25	$109.20
Purchase #4	$101.36	4.117%	$105.533	$105.53	$105.55	$105.50
Purchase #5	$180.53	8.587%	$196.0321	$196.03	$196.05	$196.00
Purchase #6	$202.64	4.819%	$212.4052	$212.41	$212.40	$212.40
Purchase #7	$61.32	6.349%	$65.2132	$65.21	$65.20	$65.20
7 purchase totals =	$1,019.91		$1,089.4236	$1,089.43	$1,089.45	$1,089.30