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	$49.98	10.156%	$55.056	$55.06	$55.05	$55.10
Purchase #2	$141.84	13.459%	$160.9302	$160.93	$160.95	$160.90
Purchase #3	$249.51	4.701%	$261.2395	$261.24	$261.25	$261.20
Purchase #4	$77.25	11.342%	$86.0117	$86.01	$86.00	$86.00
Purchase #5	$82.58	9.478%	$90.4069	$90.41	$90.40	$90.40
Purchase #6	$248.57	5.122%	$261.3018	$261.30	$261.30	$261.30
Purchase #7	$99.27	5.577%	$104.8063	$104.81	$104.80	$104.80
7 purchase totals =	$949.00		$1,019.7524	$1,019.76	$1,019.75	$1,019.70