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	$168.89	7.364%	$181.3271	$181.33	$181.35	$181.30
Purchase #2	$210.99	11.663%	$235.5978	$235.60	$235.60	$235.60
Purchase #3	$152.69	10.370%	$168.524	$168.52	$168.50	$168.50
Purchase #4	$22.58	10.859%	$25.032	$25.03	$25.05	$25.00
Purchase #5	$154.26	11.252%	$171.6173	$171.62	$171.60	$171.60
Purchase #6	$36.25	3.172%	$37.3999	$37.40	$37.40	$37.40
Purchase #7	$30.55	6.547%	$32.5501	$32.55	$32.55	$32.60
7 purchase totals =	$776.21		$852.0482	$852.05	$852.05	$852.00