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	$43.80	9.845%	$48.1121	$48.11	$48.10	$48.10
Purchase #2	$199.30	11.582%	$222.3829	$222.38	$222.40	$222.40
Purchase #3	$199.89	10.763%	$221.4042	$221.40	$221.40	$221.40
Purchase #4	$168.27	6.764%	$179.6518	$179.65	$179.65	$179.70
Purchase #5	$103.76	11.604%	$115.8003	$115.80	$115.80	$115.80
Purchase #6	$158.94	6.394%	$169.1026	$169.10	$169.10	$169.10
Purchase #7	$190.86	7.825%	$205.7948	$205.79	$205.80	$205.80
7 purchase totals =	$1,064.82		$1,162.2487	$1,162.23	$1,162.25	$1,162.30