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	$183.34	11.565%	$204.5433	$204.54	$204.55	$204.50
Purchase #2	$65.38	7.398%	$70.2168	$70.22	$70.20	$70.20
Purchase #3	$114.34	11.706%	$127.7246	$127.72	$127.70	$127.70
Purchase #4	$247.64	13.127%	$280.1477	$280.15	$280.15	$280.10
Purchase #5	$27.66	6.436%	$29.4402	$29.44	$29.45	$29.40
Purchase #6	$174.81	8.199%	$189.1427	$189.14	$189.15	$189.10
Purchase #7	$99.39	11.556%	$110.8755	$110.88	$110.90	$110.90
7 purchase totals =	$912.56		$1,012.0908	$1,012.09	$1,012.10	$1,011.90