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	$19.41	13.265%	$21.9847	$21.98	$22.00	$22.00
Purchase #2	$34.63	7.643%	$37.2768	$37.28	$37.30	$37.30
Purchase #3	$40.96	13.180%	$46.3585	$46.36	$46.35	$46.40
Purchase #4	$83.60	13.346%	$94.7573	$94.76	$94.75	$94.80
Purchase #5	$168.95	12.736%	$190.4675	$190.47	$190.45	$190.50
Purchase #6	$174.77	6.694%	$186.4691	$186.47	$186.45	$186.50
Purchase #7	$164.56	10.539%	$181.903	$181.90	$181.90	$181.90
7 purchase totals =	$686.88		$759.2169	$759.22	$759.20	$759.40