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	$173.38	4.635%	$181.4162	$181.42	$181.40	$181.40
Purchase #2	$70.30	11.745%	$78.5567	$78.56	$78.55	$78.60
Purchase #3	$33.28	5.431%	$35.0874	$35.09	$35.10	$35.10
Purchase #4	$155.63	6.648%	$165.9763	$165.98	$166.00	$166.00
Purchase #5	$73.56	6.379%	$78.2524	$78.25	$78.25	$78.30
Purchase #6	$249.32	10.514%	$275.5335	$275.53	$275.55	$275.50
Purchase #7	$105.87	3.532%	$109.6093	$109.61	$109.60	$109.60
7 purchase totals =	$861.34		$924.4318	$924.44	$924.45	$924.50