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	$205.57	11.608%	$229.4326	$229.43	$229.45	$229.40
Purchase #2	$43.48	12.171%	$48.772	$48.77	$48.75	$48.80
Purchase #3	$185.26	3.719%	$192.1498	$192.15	$192.15	$192.10
Purchase #4	$98.64	11.424%	$109.9086	$109.91	$109.90	$109.90
Purchase #5	$108.62	5.713%	$114.8255	$114.83	$114.85	$114.80
Purchase #6	$150.42	11.194%	$167.258	$167.26	$167.25	$167.30
Purchase #7	$244.53	8.353%	$264.9556	$264.96	$264.95	$265.00
7 purchase totals =	$1,036.52		$1,127.3021	$1,127.31	$1,127.30	$1,127.30