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	$233.68	12.702%	$263.362	$263.36	$263.35	$263.40
Purchase #2	$130.43	9.155%	$142.3709	$142.37	$142.35	$142.40
Purchase #3	$28.53	5.837%	$30.1953	$30.20	$30.20	$30.20
Purchase #4	$33.50	10.663%	$37.0721	$37.07	$37.05	$37.10
Purchase #5	$82.32	3.828%	$85.4712	$85.47	$85.45	$85.50
Purchase #6	$181.72	5.223%	$191.2112	$191.21	$191.20	$191.20
Purchase #7	$161.96	13.844%	$184.3817	$184.38	$184.40	$184.40
7 purchase totals =	$852.14		$934.0644	$934.06	$934.00	$934.20