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	$70.93	9.355%	$77.5655	$77.57	$77.55	$77.60
Purchase #2	$93.31	7.818%	$100.605	$100.61	$100.60	$100.60
Purchase #3	$68.82	3.251%	$71.0573	$71.06	$71.05	$71.10
Purchase #4	$249.60	8.789%	$271.5373	$271.54	$271.55	$271.50
Purchase #5	$81.85	11.478%	$91.2447	$91.24	$91.25	$91.20
Purchase #6	$223.97	4.524%	$234.1024	$234.10	$234.10	$234.10
Purchase #7	$40.46	11.859%	$45.2582	$45.26	$45.25	$45.30
7 purchase totals =	$828.94		$891.3704	$891.38	$891.35	$891.40