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	$139.25	9.349%	$152.2685	$152.27	$152.25	$152.30
Purchase #2	$161.39	4.853%	$169.2223	$169.22	$169.20	$169.20
Purchase #3	$114.95	11.432%	$128.0911	$128.09	$128.10	$128.10
Purchase #4	$31.33	7.793%	$33.7715	$33.77	$33.75	$33.80
Purchase #5	$43.82	9.813%	$48.1201	$48.12	$48.10	$48.10
Purchase #6	$224.95	13.843%	$256.0898	$256.09	$256.10	$256.10
Purchase #7	$136.36	3.770%	$141.5008	$141.50	$141.50	$141.50
7 purchase totals =	$852.05		$929.0641	$929.06	$929.00	$929.10