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	$194.88	10.624%	$215.5841	$215.58	$215.60	$215.60
Purchase #2	$72.98	7.317%	$78.3199	$78.32	$78.30	$78.30
Purchase #3	$90.87	6.507%	$96.7829	$96.78	$96.80	$96.80
Purchase #4	$203.52	6.466%	$216.6796	$216.68	$216.70	$216.70
Purchase #5	$109.82	8.139%	$118.7582	$118.76	$118.75	$118.80
Purchase #6	$40.53	7.139%	$43.4234	$43.42	$43.40	$43.40
Purchase #7	$36.80	7.581%	$39.5898	$39.59	$39.60	$39.60
7 purchase totals =	$749.40		$809.1379	$809.13	$809.15	$809.20