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	$237.40	11.377%	$264.409	$264.41	$264.40	$264.40
Purchase #2	$99.52	13.166%	$112.6228	$112.62	$112.60	$112.60
Purchase #3	$39.46	10.521%	$43.6116	$43.61	$43.60	$43.60
Purchase #4	$113.30	13.692%	$128.813	$128.81	$128.80	$128.80
Purchase #5	$86.94	13.570%	$98.7378	$98.74	$98.75	$98.70
Purchase #6	$41.87	12.629%	$47.1578	$47.16	$47.15	$47.20
Purchase #7	$159.85	13.377%	$181.2331	$181.23	$181.25	$181.20
7 purchase totals =	$778.34		$876.5851	$876.58	$876.55	$876.50