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	$230.31	10.282%	$253.9905	$253.99	$254.00	$254.00
Purchase #2	$145.98	4.310%	$152.2717	$152.27	$152.25	$152.30
Purchase #3	$81.71	11.630%	$91.2129	$91.21	$91.20	$91.20
Purchase #4	$49.39	7.397%	$53.0434	$53.04	$53.05	$53.00
Purchase #5	$114.96	5.277%	$121.0264	$121.03	$121.05	$121.00
Purchase #6	$196.56	9.628%	$215.4848	$215.48	$215.50	$215.50
Purchase #7	$156.61	11.655%	$174.8629	$174.86	$174.85	$174.90
7 purchase totals =	$975.52		$1,061.8926	$1,061.88	$1,061.90	$1,061.90