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	$247.91	4.526%	$259.1304	$259.13	$259.15	$259.10
Purchase #2	$24.33	13.367%	$27.5822	$27.58	$27.60	$27.60
Purchase #3	$40.98	5.760%	$43.3404	$43.34	$43.35	$43.30
Purchase #4	$11.38	7.346%	$12.216	$12.22	$12.20	$12.20
Purchase #5	$73.62	12.253%	$82.6407	$82.64	$82.65	$82.60
Purchase #6	$88.43	3.772%	$91.7656	$91.77	$91.75	$91.80
Purchase #7	$130.84	12.834%	$147.632	$147.63	$147.65	$147.60
7 purchase totals =	$617.49		$664.3073	$664.31	$664.35	$664.20