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	$133.55	10.326%	$147.3404	$147.34	$147.35	$147.30
Purchase #2	$35.69	4.798%	$37.4024	$37.40	$37.40	$37.40
Purchase #3	$105.93	3.283%	$109.4077	$109.41	$109.40	$109.40
Purchase #4	$56.65	6.551%	$60.3611	$60.36	$60.35	$60.40
Purchase #5	$111.65	6.258%	$118.6371	$118.64	$118.65	$118.60
Purchase #6	$134.64	12.813%	$151.8914	$151.89	$151.90	$151.90
Purchase #7	$123.87	10.414%	$136.7698	$136.77	$136.75	$136.80
7 purchase totals =	$701.98		$761.8099	$761.81	$761.80	$761.80