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	$100.39	10.539%	$110.9701	$110.97	$110.95	$111.00
Purchase #2	$42.32	7.670%	$45.5659	$45.57	$45.55	$45.60
Purchase #3	$147.60	9.263%	$161.2722	$161.27	$161.25	$161.30
Purchase #4	$162.30	8.124%	$175.4853	$175.49	$175.50	$175.50
Purchase #5	$244.28	7.762%	$263.241	$263.24	$263.25	$263.20
Purchase #6	$209.27	6.854%	$223.6134	$223.61	$223.60	$223.60
Purchase #7	$27.42	13.172%	$31.0318	$31.03	$31.05	$31.00
7 purchase totals =	$933.58		$1,011.1797	$1,011.18	$1,011.15	$1,011.20