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	$176.44	6.722%	$188.3003	$188.30	$188.30	$188.30
Purchase #2	$97.68	13.642%	$111.0055	$111.01	$111.00	$111.00
Purchase #3	$33.63	6.294%	$35.7467	$35.75	$35.75	$35.70
Purchase #4	$164.74	10.119%	$181.41	$181.41	$181.40	$181.40
Purchase #5	$115.91	3.611%	$120.0955	$120.10	$120.10	$120.10
Purchase #6	$173.97	11.821%	$194.535	$194.54	$194.55	$194.50
Purchase #7	$96.56	7.190%	$103.5027	$103.50	$103.50	$103.50
7 purchase totals =	$858.93		$934.5957	$934.61	$934.60	$934.50