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	$219.65	3.847%	$228.0999	$228.10	$228.10	$228.10
Purchase #2	$72.75	13.766%	$82.7648	$82.76	$82.75	$82.80
Purchase #3	$233.45	6.799%	$249.3223	$249.32	$249.30	$249.30
Purchase #4	$196.91	9.721%	$216.0516	$216.05	$216.05	$216.10
Purchase #5	$35.84	8.167%	$38.7671	$38.77	$38.75	$38.80
Purchase #6	$21.46	3.841%	$22.2843	$22.28	$22.30	$22.30
Purchase #7	$132.89	13.160%	$150.3783	$150.38	$150.40	$150.40
7 purchase totals =	$912.95		$987.6683	$987.66	$987.65	$987.80