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	$194.69	3.281%	$201.0778	$201.08	$201.10	$201.10
Purchase #2	$83.75	7.825%	$90.3034	$90.30	$90.30	$90.30
Purchase #3	$166.25	12.421%	$186.8999	$186.90	$186.90	$186.90
Purchase #4	$95.72	3.757%	$99.3162	$99.32	$99.30	$99.30
Purchase #5	$45.58	13.604%	$51.7807	$51.78	$51.80	$51.80
Purchase #6	$128.33	11.152%	$142.6414	$142.64	$142.65	$142.60
Purchase #7	$202.52	6.601%	$215.8883	$215.89	$215.90	$215.90
7 purchase totals =	$916.84		$987.9077	$987.91	$987.95	$987.90