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	$232.58	4.116%	$242.153	$242.15	$242.15	$242.20
Purchase #2	$179.98	9.318%	$196.7505	$196.75	$196.75	$196.80
Purchase #3	$108.39	6.312%	$115.2316	$115.23	$115.25	$115.20
Purchase #4	$241.72	6.843%	$258.2609	$258.26	$258.25	$258.30
Purchase #5	$166.46	3.854%	$172.8754	$172.88	$172.90	$172.90
Purchase #6	$80.88	10.367%	$89.2648	$89.26	$89.25	$89.30
Purchase #7	$104.92	6.531%	$111.7723	$111.77	$111.75	$111.80
7 purchase totals =	$1,114.93		$1,186.3085	$1,186.30	$1,186.30	$1,186.50