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	$242.30	4.809%	$253.9522	$253.95	$253.95	$254.00
Purchase #2	$116.96	8.632%	$127.056	$127.06	$127.05	$127.10
Purchase #3	$76.88	12.522%	$86.5069	$86.51	$86.50	$86.50
Purchase #4	$61.46	5.817%	$65.0351	$65.04	$65.05	$65.00
Purchase #5	$114.25	3.740%	$118.523	$118.52	$118.50	$118.50
Purchase #6	$141.81	13.441%	$160.8707	$160.87	$160.85	$160.90
Purchase #7	$220.71	10.346%	$243.5447	$243.54	$243.55	$243.50
7 purchase totals =	$974.37		$1,055.4886	$1,055.49	$1,055.45	$1,055.50