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	$156.50	7.763%	$168.6491	$168.65	$168.65	$168.60
Purchase #2	$154.91	7.116%	$165.9334	$165.93	$165.95	$165.90
Purchase #3	$201.49	5.112%	$211.7902	$211.79	$211.80	$211.80
Purchase #4	$133.30	5.443%	$140.5555	$140.56	$140.55	$140.60
Purchase #5	$218.40	10.354%	$241.0131	$241.01	$241.00	$241.00
Purchase #6	$72.86	11.334%	$81.118	$81.12	$81.10	$81.10
Purchase #7	$130.31	9.270%	$142.3897	$142.39	$142.40	$142.40
7 purchase totals =	$1,067.77		$1,151.4490	$1,151.45	$1,151.45	$1,151.40