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	$28.56	13.273%	$32.3508	$32.35	$32.35	$32.40
Purchase #2	$197.51	11.144%	$219.5205	$219.52	$219.50	$219.50
Purchase #3	$235.36	13.718%	$267.6467	$267.65	$267.65	$267.60
Purchase #4	$99.90	5.513%	$105.4075	$105.41	$105.40	$105.40
Purchase #5	$97.50	5.251%	$102.6197	$102.62	$102.60	$102.60
Purchase #6	$189.95	13.370%	$215.3463	$215.35	$215.35	$215.30
Purchase #7	$59.76	11.126%	$66.4089	$66.41	$66.40	$66.40
7 purchase totals =	$908.54		$1,009.3004	$1,009.31	$1,009.25	$1,009.20