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	$196.73	6.742%	$209.9935	$209.99	$210.00	$210.00
Purchase #2	$81.84	13.677%	$93.0333	$93.03	$93.05	$93.00
Purchase #3	$39.72	9.232%	$43.387	$43.39	$43.40	$43.40
Purchase #4	$72.54	8.595%	$78.7748	$78.77	$78.75	$78.80
Purchase #5	$173.96	11.861%	$194.5934	$194.59	$194.60	$194.60
Purchase #6	$99.30	6.496%	$105.7505	$105.75	$105.75	$105.80
Purchase #7	$169.71	9.330%	$185.5439	$185.54	$185.55	$185.50
7 purchase totals =	$833.80		$911.0764	$911.06	$911.10	$911.10