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	$162.84	5.121%	$171.179	$171.18	$171.20	$171.20
Purchase #2	$30.30	3.794%	$31.4496	$31.45	$31.45	$31.40
Purchase #3	$156.28	7.234%	$167.5853	$167.59	$167.60	$167.60
Purchase #4	$80.72	5.319%	$85.0135	$85.01	$85.00	$85.00
Purchase #5	$135.94	6.514%	$144.7951	$144.80	$144.80	$144.80
Purchase #6	$232.38	9.155%	$253.6544	$253.65	$253.65	$253.70
Purchase #7	$181.56	10.455%	$200.5421	$200.54	$200.55	$200.50
7 purchase totals =	$980.02		$1,054.2190	$1,054.22	$1,054.25	$1,054.20