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	$98.67	12.618%	$111.1202	$111.12	$111.10	$111.10
Purchase #2	$91.27	5.354%	$96.1566	$96.16	$96.15	$96.20
Purchase #3	$35.26	5.818%	$37.3114	$37.31	$37.30	$37.30
Purchase #4	$54.93	12.712%	$61.9127	$61.91	$61.90	$61.90
Purchase #5	$211.82	6.397%	$225.3701	$225.37	$225.35	$225.40
Purchase #6	$147.70	9.472%	$161.6901	$161.69	$161.70	$161.70
Purchase #7	$133.44	12.724%	$150.4189	$150.42	$150.40	$150.40
7 purchase totals =	$773.09		$843.9800	$843.98	$843.90	$844.00