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	$237.56	3.284%	$245.3615	$245.36	$245.35	$245.40
Purchase #2	$49.91	9.503%	$54.6529	$54.65	$54.65	$54.70
Purchase #3	$173.36	9.500%	$189.8292	$189.83	$189.85	$189.80
Purchase #4	$175.44	3.268%	$181.1734	$181.17	$181.15	$181.20
Purchase #5	$90.50	8.784%	$98.4495	$98.45	$98.45	$98.40
Purchase #6	$179.32	6.339%	$190.6871	$190.69	$190.70	$190.70
Purchase #7	$212.63	5.751%	$224.8584	$224.86	$224.85	$224.90
7 purchase totals =	$1,118.72		$1,185.0120	$1,185.01	$1,185.00	$1,185.10