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	$120.58	13.755%	$137.1658	$137.17	$137.15	$137.20
Purchase #2	$195.66	10.192%	$215.6017	$215.60	$215.60	$215.60
Purchase #3	$90.54	3.365%	$93.5867	$93.59	$93.60	$93.60
Purchase #4	$129.28	11.765%	$144.4898	$144.49	$144.50	$144.50
Purchase #5	$112.67	10.553%	$124.5601	$124.56	$124.55	$124.60
Purchase #6	$172.27	10.873%	$191.0009	$191.00	$191.00	$191.00
Purchase #7	$156.76	7.183%	$168.0201	$168.02	$168.00	$168.00
7 purchase totals =	$977.76		$1,074.4251	$1,074.43	$1,074.40	$1,074.50