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	$181.40	5.270%	$190.9598	$190.96	$190.95	$191.00
Purchase #2	$159.48	8.249%	$172.6355	$172.64	$172.65	$172.60
Purchase #3	$220.40	9.126%	$240.5137	$240.51	$240.50	$240.50
Purchase #4	$223.75	3.145%	$230.7869	$230.79	$230.80	$230.80
Purchase #5	$154.83	6.135%	$164.3288	$164.33	$164.35	$164.30
Purchase #6	$38.65	13.819%	$43.991	$43.99	$44.00	$44.00
Purchase #7	$90.31	6.364%	$96.0573	$96.06	$96.05	$96.10
7 purchase totals =	$1,068.82		$1,139.2730	$1,139.28	$1,139.30	$1,139.30