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	$49.91	4.275%	$52.0437	$52.04	$52.05	$52.00
Purchase #2	$157.26	3.242%	$162.3584	$162.36	$162.35	$162.40
Purchase #3	$209.45	6.250%	$222.5406	$222.54	$222.55	$222.50
Purchase #4	$133.99	6.520%	$142.7261	$142.73	$142.75	$142.70
Purchase #5	$37.34	11.289%	$41.5553	$41.56	$41.55	$41.60
Purchase #6	$152.28	10.439%	$168.1765	$168.18	$168.20	$168.20
Purchase #7	$234.43	3.735%	$243.186	$243.19	$243.20	$243.20
7 purchase totals =	$974.66		$1,032.5866	$1,032.60	$1,032.65	$1,032.60