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	$132.52	7.817%	$142.8791	$142.88	$142.90	$142.90
Purchase #2	$45.71	11.693%	$51.0549	$51.05	$51.05	$51.10
Purchase #3	$201.54	8.449%	$218.5681	$218.57	$218.55	$218.60
Purchase #4	$123.97	6.782%	$132.3776	$132.38	$132.40	$132.40
Purchase #5	$118.93	12.781%	$134.1304	$134.13	$134.15	$134.10
Purchase #6	$142.35	9.820%	$156.3288	$156.33	$156.35	$156.30
Purchase #7	$200.46	9.516%	$219.5358	$219.54	$219.55	$219.50
7 purchase totals =	$965.48		$1,054.8747	$1,054.88	$1,054.95	$1,054.90