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	$116.43	9.194%	$127.1346	$127.13	$127.15	$127.10
Purchase #2	$227.89	5.173%	$239.6787	$239.68	$239.70	$239.70
Purchase #3	$74.76	10.422%	$82.5515	$82.55	$82.55	$82.60
Purchase #4	$153.53	7.291%	$164.7239	$164.72	$164.70	$164.70
Purchase #5	$228.73	11.357%	$254.7069	$254.71	$254.70	$254.70
Purchase #6	$46.41	10.468%	$51.2682	$51.27	$51.25	$51.30
Purchase #7	$89.33	7.813%	$96.3094	$96.31	$96.30	$96.30
7 purchase totals =	$937.08		$1,016.3732	$1,016.37	$1,016.35	$1,016.40