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	$20.33	8.289%	$22.0152	$22.02	$22.00	$22.00
Purchase #2	$10.71	4.477%	$11.1895	$11.19	$11.20	$11.20
Purchase #3	$115.90	6.479%	$123.4092	$123.41	$123.40	$123.40
Purchase #4	$72.71	7.420%	$78.1051	$78.11	$78.10	$78.10
Purchase #5	$243.39	13.518%	$276.2915	$276.29	$276.30	$276.30
Purchase #6	$61.27	10.417%	$67.6525	$67.65	$67.65	$67.70
Purchase #7	$212.83	13.751%	$242.0963	$242.10	$242.10	$242.10
7 purchase totals =	$737.14		$820.7593	$820.77	$820.75	$820.80