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	$168.98	3.294%	$174.5462	$174.55	$174.55	$174.50
Purchase #2	$18.76	8.331%	$20.3229	$20.32	$20.30	$20.30
Purchase #3	$84.60	8.822%	$92.0634	$92.06	$92.05	$92.10
Purchase #4	$115.93	13.493%	$131.5724	$131.57	$131.55	$131.60
Purchase #5	$58.68	12.366%	$65.9364	$65.94	$65.95	$65.90
Purchase #6	$60.50	11.204%	$67.2784	$67.28	$67.30	$67.30
Purchase #7	$44.47	12.723%	$50.1279	$50.13	$50.15	$50.10
7 purchase totals =	$551.92		$601.8476	$601.85	$601.85	$601.80